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1
Sovilla, B., M. Kern, and M. Schaer. "Slow drag in wet-snow avalanche flow." Journal of Glaciology 56, no. 198 (2010): 587–92. http://dx.doi.org/10.3189/002214310793146287.
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AbstractWe report impact pressures exerted by three wet-snow avalanches on a pylon equipped with piezoelectric load cells. These pressures were considerably higher than those predicted by conventional avalanche engineering guidelines. The time-averaged pressure linearly increased with the immersion depth of the load cells and it was about eight times larger than the hydrostatic snow pressure. At the same immersion depth, the pressures were very similar for all three avalanches and no dependency between avalanche velocity and pressure was apparent. The pressure time series were characterized by large fluctuations. For all immersion depths and for all avalanches, the standard deviations of the fluctuations were, on average, about 20% of the mean value. We compare our observations with results of slow-drag granular experiments, where similar behavior has been explained by formation and destruction of chain structures due to jamming of granular material around the pylon, and we propose the same mechanism as a possible microscale interpretation of our observations.
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Squire, L. C., and S. H. Nasser. "Cavity drag at transonic speeds." Aeronautical Journal 97, no. 967 (1993): 247–56. http://dx.doi.org/10.1017/s000192400002635x.
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AbstractThis paper presents the results of an investigation of the flow around rectangular and chamfered cavities at high subsonic and low supersonic speeds. Pressures measured on the faces of the cavities are integrated to find the pressure drag of the cavities. The types of cavity tested range from simple sawcuts to cavities so long that the two ends can be regarded as independent and the results for these are compared with the sum of the drags of isolated forward and rear facing steps.Although the Reynolds numbers of the tests are similar to those in flight conditions the maximum depth of the cavities tested is only 6 mm so that the pressure resolution on the vertical faces of the cavities is limited. In spite of this it is estimated that the maximum error in the drag of any particular cavity is less than the skin friction drag on a smooth surface equal in area to half the plan area of the cavity.
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Emeis, S. "Surface pressure distribution and pressure drag on mountains." Meteorology and Atmospheric Physics 43, no. 1-4 (1990): 173–85. http://dx.doi.org/10.1007/bf01028120.
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Oh, Jae-Sung, Taehak Kang, Seokgyun Ham, et al. "Numerical Analysis of Aerodynamic Characteristics of Hyperloop System." Energies 12, no. 3 (2019): 518. http://dx.doi.org/10.3390/en12030518.
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The Hyperloop system is a new concept that allows a train to travel through a near-vacuum tunnel at transonic speeds. Aerodynamic drag is one of the most important factors in analyzing such systems. The blockage ratio (BR), pod speed/length, tube pressure, and temperature affect the aerodynamic drag, but the specific relationships between the drag and these parameters have not yet been comprehensively examined. In this study, we investigated the flow phenomena of a Hyperloop system, focusing on the effects of changes in the above parameters. Two-dimensional axisymmetric simulations were performed in a large parameter space covering various BR values (0.25, 0.36), pod lengths (10.75–86 m), pod speeds (50–350 m/s), tube pressures (~100–1000 Pa), and tube temperatures (275–325 K). As BR increased, the pressure drag was significantly affected. This is because of the smaller critical Mach number for a larger BR. As the pod length increased, the total drag and pressure drag did not change significantly, but there was a considerable influence on the friction drag. As the pod speed increased, strong shock waves occurred near the end of the pod. At this point, the flows around the pod were severely choked at both BR values, and the ratio of the pressure drag to the total drag converged to its saturation level. At tube pressures above 500 Pa, the friction drag increased significantly under the rapidly increased turbulence intensity near the pod surface. High tube temperatures increase the speed of sound, and this reduces the Mach number for the same pod speed, consequently delaying the onset of choking and reducing the aerodynamic drag. The results presented in this study are applicable to the fundamental design of the proposed Hyperloop system.
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Wijesekera, H. W., E. Jarosz, W. J. Teague, et al. "Measurements of Form and Frictional Drags over a Rough Topographic Bank." Journal of Physical Oceanography 44, no. 9 (2014): 2409–32. http://dx.doi.org/10.1175/jpo-d-13-0230.1.
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Abstract Pressure differences across topography generate a form drag that opposes the flow in the water column, and viscous and pressure forces acting on roughness elements of the topographic surface generate a frictional drag on the bottom. Form drag and bottom roughness lengths were estimated over the East Flower Garden Bank (EFGB) in the Gulf of Mexico by combining an array of bottom pressure measurements and profiles of velocity and turbulent kinetic dissipation rates. The EFGB is a coral bank about 6 km wide and 10 km long located at the shelf edge that rises from 100-m water depth to about 18 m below the sea surface. The average frictional drag coefficient over the entire bank was estimated as 0.006 using roughness lengths that ranged from 0.001 cm for relatively smooth portions of the bank to 1–10 cm for very rough portions over the corals. The measured form drag over the bank showed multiple time-scale variability. Diurnal tides and low-frequency motions with periods ranging from 4 to 17 days generated form drags of about 2000 N m−1 with average drag coefficients ranging between 0.03 and 0.22, which are a factor of 5–35 times larger than the average frictional drag coefficient. Both linear wave and quadratic drag laws have similarities with the observed form drag. The form drag is an important flow retardation mechanism even in the presence of the large frictional drag associated with coral reefs and requires parameterization.
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Zhang, Li, Zhenghong Gao, and Yiming Du. "Study on Cruise Drag Characteristics of Low Drag Normal Layout Civil Aircraft." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 38, no. 3 (2020): 580–88. http://dx.doi.org/10.1051/jnwpu/20203830580.
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This paper focus on the wing shape related drag reduction measures of normal layout civil aircraft, through the drag reduction to improve the aircraft performance. Mainly by the laminar flow wing to reduce skin drag and weak shock wave wing to reduce shock drag, to keep a section of laminar zone on the wing leading edge to reduce skin drag, the wing profile's pressure distribution transit from the middle part's tonsure pressure zone to the trailing edge's inverse pressure gradient zone gentle to reduce the shock drag. The wing body junction plus the body belly fairing to increase the junction flow velocity, through increase flow velocity to weak the boundary layer stacked at the junction, improve the drag performance. The blended winglet to reduce the wing tip induced drag, study the shape parameters impact on the drag reduction, longitudinal moment and directional moment, attain the winglet model with drag reduction effect, suitable pitching moment and directional moment. For the wing body fairing have significant impact on the wing shape lower surface pressure distribution, the winglet have important impact on the wing tip flow, so the single part drag reduction measure is not feasible, need to carry out integrated drag reduction study on the wing related three drag reduction measures, and study the drag reduction measure's drag reduction decrement, put a reference for the normal layout civil aircraft's drag reduction. Through the above drag reduction measure's assessment attain the effect of drag reduction and rising the normal layout civil aircraft's cruise ratio, improving the cruise performance.
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Zheng, Qiu Ya, and San Yang Liu. "Drag Prediction on DLR-F6 Wing-Body Configuration." Applied Mechanics and Materials 110-116 (October 2011): 1506–11. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.1506.
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This paper mainly investigate the accuracy of the computed drag on the DLR-F6 Wing-Body configuration, and analyze effect of grid and the turbulence models including the Spalart-Allmaras model, Wilcox’s k-ω model and Menter shear-stress transport model on aerodynamic forces for wing-body configuration. The computed results show that grid refinement has little effect on the pressure distributions, significant effect on drag. The turbulence models have certain effects on the pressure distributions, especially positions of the shock wave. They have obvious effects on drag, particularly friction drag. This study shows that performing the CFD calculation at the same angle-of-attack as experiment resulted in good comparisons with wing surface pressures.
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Prokash Chandra Roy, Arafater Rahman, and Mihir Ranjan Halder. "Numerical Investigation of Aerodynamic Characteristics of Hyperloop System Using Optimized Capsule Design." International Journal of Automotive and Mechanical Engineering 19, no. 4 (2023): 10132–43. http://dx.doi.org/10.15282/ijame.19.4.2022.10.0784.
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As a consequence of research on developing a speedy transportation system, Hyperloop is one of the best solutions now as smaller resistant forces are developed on the capsule body compared to conventional ground transportation systems due to movement in a vacuum and no contact with the ground. In this study, a capsule of an elliptical-shaped head and semicircular-shaped rear was chosen for analysis. Aerodynamic drags were calculated at different evacuated tunnel pressures. The computational regime was a 360 meters long tunnel. The inlet and outlet were pressure far-field boundaries while the wall was moving, with a Blockage Ratio (BR) of 0.36. Characteristics of different regions were identified in choked conditions. The drag was found to be lesser than the capsule of semicircular ends at different speeds. The pressure drag and friction drag were increased with the increase in velocity in the same tunnel pressure. By investigating different flow regions, it was found that a series of rhomboidal-shaped shock waves appear at high speeds. The formation and nature of this shock wave were also investigated, and found that it is caused due to shock wave and expansion wave interaction that results in the fall of pressure and temperature in the wake region.
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Mr., Gaurav p. Rana* Mr. Mayurkumar s. Rana Mr. Romil j. Champaneria Mr. Saurang n. Patel Mr. Mitul J. Barot. "ANALYSIS AND SIMULATION OF COOLING TOWERFAN BLADE: AN OVERVIEW." ANALYSIS AND SIMULATION OF COOLING TOWERFAN BLADE: AN OVERVIEW 6, no. 1 (2017): 242–44. https://doi.org/10.5281/zenodo.246609.
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Cooling tower fan wings are the rotating surface with the chosen aerofoil sections. The efficiency as well as the performance of an fan mostly depends on the aerodynamic characteristics i.e. e.g. lift,drags,lifts to drag ratio ,etc of the blades besides many factors the effects of blade where are also crucial to cooling tower fan performance. This project represents the experimental investigation to explore better aerodynamic performance by increase radial velocity of fan. The aerofoil is tested in closed circuit wind tunnel. The static pressure at different angle of attack are measured from rapper and lower surface of the aerofoil through different pressure tapings by using a multi tube water manometer from the static pressure distribution, lift coefficient, drag coefficient and lift to drag ratio of aerofoil is analysed.
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Bing, Tan, Lu Peng, Li Zhijun, and Li Runling. "Form drag on pressure ridges and drag coefficient in the northwestern Weddell Sea, Antarctica, in winter." Annals of Glaciology 54, no. 62 (2013): 133–38. http://dx.doi.org/10.3189/2013aog62a092.
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AbstractSurface elevation data for sea ice in the northwesternty - Weddell Sea, Antarctica, collected by a helicopter-borne laser altimeter during the Winter Weddell Outflow Study 2006, were used to estimate the form drag on pressure ridges and its contribution to the total wind drag, and the air-ice drag coefficient at a reference height of 10 m under neutral stability conditions (Cdn(10)). This was achieved by partitioning the total wind drag into two components: form drag on pressure ridges and skin drag over rough sea-ice surfaces. The results reveal that for the compacted ice field, the contribution of form drag on pressure ridges to the total wind drag increases with increasing ridging intensity Ri (where Ri is the ratio of mean ridge height to spacing), while the contribution decreases with increasing roughness length. There is also an increasing trend in the air-ice drag coefficient Cdn(10) as ridging intensity Ri increases. However, as roughness length increases, Cdn(10) increases at lower ridging intensities (Ri < 0.023) but decreases at lower ridging intensities (0.023 < Ri < 0.05). These opposing trends are mainly caused by the dominance of the form drag on pressure ridges and skin drag over rough ice surfaces. Generally, the form drag becomes dominant only when the ridging intensity is sufficiently large, while the skin drag is the dominant component at relatively larger ridging intensities. These results imply that a large value of Cdn(10) is caused not only by the form drag on pressure ridges, but also by the skin drag over rough ice surfaces. Additionally, the estimated drag coefficients are consistent with reported measurements in the northwestern Weddell Sea, further demonstrating the feasibility of the drag partition model.
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Williams, Dr Daniel, and Dr Alexei M. Ivanov. "OPTIMIZING VEHICLE DESIGN FOR EFFICIENCY: PRESSURE GRADIENT AND AERODYNAMICS EVALUATION USING CFD." International Journal of Research in Engineering 3, no. 1 (2023): 1–5. https://doi.org/10.55640/ijre-03-01-01.
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The evaluation of aerodynamics plays a critical role in the performance, fuel efficiency, and stability of vehicles. Understanding how air interacts with the surface of a moving vehicle is essential to optimize designs for minimal drag and improved handling. This study investigates the aerodynamic behavior and pressure gradient distribution around a moving vehicle using computational fluid dynamics (CFD) simulations. The objective is to analyze how different flow conditions impact the pressure distribution on the vehicle's body, which, in turn, affects the drag force and overall vehicle performance. The research specifically focuses on identifying regions of high-pressure gradients, which are crucial in understanding vehicle stability, drag, and the potential for turbulence. Results demonstrate significant variations in pressure distribution depending on vehicle speed, shape, and surrounding environment. The study concludes by proposing potential design modifications that could reduce drag and improve vehicle efficiency.
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Mohammadi, A., and J. M. Floryan. "Pressure losses in grooved channels." Journal of Fluid Mechanics 725 (May 14, 2013): 23–54. http://dx.doi.org/10.1017/jfm.2013.184.
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AbstractThe effects of small-amplitude, two-dimensional grooves on pressure losses in a laminar channel flow have been analysed. Grooves with an arbitrary shape and an arbitrary orientation with respect to the flow direction have been considered. It has been demonstrated that losses can be expressed as a superposition of two parts, one associated with change in the mean positions of the walls and one induced by flow modulations associated with the geometry of the grooves. The former effect can be determined analytically, while the latter has to be determined numerically and can be captured with an acceptable accuracy using reduced-order geometry models. Projection of the wall shape onto a Fourier space has been used to generate such a model. It has been found that in most cases replacement of the actual wall geometry with the leading mode of the relevant Fourier expansion permits determination of pressure losses with an error of less than 10 %. Detailed results are given for sinusoidal grooves for the range of parameters of practical interest. These results describe the performance of arbitrary grooves with the accuracy set by the properties of the reduced-order geometry model and are exact for sinusoidal grooves. The results show a strong dependence of the pressure losses on the groove orientation. Longitudinal grooves produce the smallest drag, and oblique grooves with an inclination angle of ${\sim }42\textdegree $ exhibit the largest flow turning potential. Detailed analyses of the extreme cases, i.e. transverse and longitudinal grooves, have been carried out. For transverse grooves with small wavenumbers, the dominant part of the drag is produced by shear, while the pressure form drag and the pressure interaction drag provide minor contributions. For the same grooves with large wavenumbers, the stream lifts up above the grooves due to their blocking effect, resulting in a change in the mechanics of drag formation: the contributions of shear decrease while the contributions of the pressure interaction drag increase, leading to an overall drag increase. In the case of longitudinal grooves, drag is produced by shear, and its rearrangement results in a drag decrease for long-wavelength grooves in spite of an increase of the wetted surface area. An increase of the wavenumber leads to the fluid being squeezed from the troughs and the stream being forced to lift up above the grooves. The shear is nearly eliminated from a large fraction of the wall but the overall drag increases due to reduction of the effective channel opening. It is shown that properly structured grooves are able to eliminate wall shear from the majority of the wetted surface area regardless of the groove orientation, thus exhibiting the potential for the creation of drag-reducing surfaces. Such surfaces can become practicable if a method for elimination of the undesired pressure and shear peaks through proper groove shaping can be found.
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Smith, Ronald B. "The wind farm pressure field." Wind Energy Science 9, no. 1 (2024): 253–61. http://dx.doi.org/10.5194/wes-9-253-2024.
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Abstract. The disturbed atmospheric pressure near a wind farm arises from the turbine drag forces in combination with vertical confinement associated with atmospheric stability. These pressure gradients slow the wind upstream, deflect the air laterally, weaken the flow deceleration over the farm, and modify the farm wake recovery. Here, we describe the airflow and pressure disturbance near a wind farm under typical stability conditions and, alternatively, with the simplifying assumption of a rigid lid. The rigid lid case clarifies the cause of the pressure disturbance and its close relationship to wind farm drag. The key to understanding the rigid lid model is the proof that the pressure field p(x,y) is a harmonic function almost everywhere. It follows that the maximum and minimum pressure occur at the front and back edge of the farm. Over the farm, the favorable pressure gradient is constant and significantly offsets the turbine drag. Upwind and downwind of the farm, the pressure field is a dipole given by p(x,y)≈Axr-2, where the coefficient A is proportional to the total farm drag. Two derivations of this law are given. Field measurements of pressure can be used to find the coefficient A and thus to estimate total farm drag.
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Daas, Mutaz, and Derek Bleyle. "Influence of Liquid Viscosity on the Pressure Loss and the Effectiveness of Drag-Reducing Agents in Horizontal Slug Flow." Journal of Energy Resources Technology 127, no. 2 (2005): 149–52. http://dx.doi.org/10.1115/1.1855327.
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Measurements of drag reduction in two-phase oil-gas slug flow are presented in this study. Two types of oil with markedly different viscosities were examined in 10-cm inner diameter horizontal pipes to evaluate the influence of oil viscosity on the total pressure loss and the effectiveness of drag-reducing agents (DRAs) in reducing the pressure drop in slug flow. The total pressure drop in the 50-cP oil was always more significant than in the 2.5-cP oil, especially when increasing the gas flow rate. However, the DRA was more effective in reducing the total pressure drop in the 2.5-cP oil. Furthermore, increasing liquid velocity, thus increasing liquid volume fraction, resulted in an increase in the DRA effectiveness for both oils.
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Huang, Lin Jie, and P. S. Ayyaswamy. "Drag Coefficients Associated With a Moving Drop Experiencing Condensation." Journal of Heat Transfer 109, no. 4 (1987): 1003–6. http://dx.doi.org/10.1115/1.3248169.
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For a moving liquid drop experiencing condensation, three different drag coefficients govern the motion and the transport. These coefficients are associated with friction, pressure, and condensation. Unlike situations involving the motion of a rigid sphere or a liquid drop without the presence of condensation, there is a large pressure recovery in the rear of a moving drop experiencing condensation. As a consequence, the pressure drag coefficient exhibits interesting behavior. While the coefficients for the friction drag and the condensation drag increase with the level of condensation, the pressure drag coefficient decreases rapidly. In this note, the roles played by the various drag forces in condensing situations are delineated. Results for the variation of average condensation heat transfer with vertical-fall height of the drop are presented.
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Zhou, Hong-Gen, Chang-Feng Jia, Gui-Zhong Tian, Xiao-Ming Feng, and Dong-Liang Fan. "Numerical Analysis of Drag Reduction Characteristics of Biomimetic Puffer Skin: Effect of Spinal Height and Tilt Angle." Journal of Nanoscience and Nanotechnology 21, no. 9 (2021): 4615–24. http://dx.doi.org/10.1166/jnn.2021.19145.
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Based on the migratory phenomenon of the puffer and the cone-shaped structures on its skin, the effects of spinal height and tilt angle on the drag reduction characteristics is presented by numerical simulation in this paper. The results show that the trend of total drag reduction efficiency changes from slow growth to a remarkable decline, while the viscous drag reduction efficiency changes from an obvious increase to steady growth. The total and viscous drag reduction efficiencies are 19.5% and 31.8%, respectively. In addition, with the increase in tilt angle, the total drag reduction efficiency decreases gradually; the viscous drag reduction efficiency first increases and then decreases, finally tending to be stable; and the total and viscous drag reduction efficiency reaches 20.7% and 26.7%, respectively. The flow field results indicate that the pressure drag mainly originates at the front row of the spines and that the total pressure drag can be effectively controlled by reducing the former pressure drag. With the increase in low-speed fluid and the reduction in the near-wall fluid velocity gradient, the viscous drag can be weakened. Nevertheless, the drag reduction effect is achieved only when the decrement of viscous drag is greater than the increment of pressure drag. This work can serve as a theoretical basis for optimizing the structure and distribution parameters of spines on bionic non-smooth surfaces.
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Wang, Ying Fei, San Peng Deng, Bo Chen, and Lin Ling Zhang. "Design of Pneumatic Parachute-Packing Machine." Advanced Materials Research 989-994 (July 2014): 3286–89. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.3286.
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As ground support equipment, drag parachute packing machine is used for packaging aircraft drag parachute. It is driven by high-pressure inert gas. Drag parachute will be compacted in the cylinder loading institution by high pressure. The overall structure of drag parachute packing machine is designed. The finite element analysis and structure optimization of drag parachute packing manipulator is completed. The pneumatic control system is designed. It provides an approach for drag parachute packing technology.
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Li, Zhiping, Yueren Zuo, Haideng Zhang, et al. "A Numerical Study on the Influence of Transverse Grooves on the Aerodynamic Performance of Micro Air Vehicles Airfoils." Applied Sciences 13, no. 22 (2023): 12371. http://dx.doi.org/10.3390/app132212371.
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Micro Air Vehicles (MAVs) airfoils usually operate at low Reynolds number conditions, where viscous drag will consume a large amount of propulsion power. Due to the small dimensions, many drag reduction methods have failed, resulting in limited current research. To develop an effective method of reducing viscous drag, transverse grooves were placed on the surface of MAVs airfoils in this study, and a numerical investigation was implemented to uncover the corresponding flow control law as well as the mechanism. Research has shown that transverse grooves have an impact on the drag and lift of airfoils. For drag, properly sized transverse grooves have the effect of reducing drag, but under high adverse pressure gradients or when the continuous arrangement of grooves is excessive, the optimal drag reduction effect achieved by the grooves is weakened, and even the drag increases due to the significant increase in pressure difference. In severe cases, it may also cause strong flow separation, which is not conducive to MAV flight. For lift, the boundary vortex in the groove has the ability to reduce the static pressure near the groove. However, high adverse pressure gradients or too many grooves will thicken the boundary layer and increase the blockage effect, resulting in a large static pressure on the grooved side of the airfoil (with an increase in drag). From the perspective of circulation, the static pressure changes on the suction and pressure surfaces have opposite effects on lift. Considering the comprehensive aerodynamic performance of the airfoil, we designed a high lift-to-drag ratio airfoil with grooves, which increased the lift-to-drag ratio by 33.747% compared to the smooth airfoil. Based on the conclusions, we proposed preliminary design criteria for grooved airfoils, providing guidance for subsequent research and applications.
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Warner, Sally J., Parker MacCready, James N. Moum, and Jonathan D. Nash. "Measurement of Tidal Form Drag Using Seafloor Pressure Sensors." Journal of Physical Oceanography 43, no. 6 (2013): 1150–72. http://dx.doi.org/10.1175/jpo-d-12-0163.1.
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Abstract As currents flow over rough topography, the pressure difference between the up- and downstream sides results in form drag—a force that opposes the flow. Measuring form drag is valuable because it can be used to estimate the loss of energy from currents as they interact with topography. An array of bottom pressure sensors was used to measure the tidal form drag on a sloping ridge in 200 m of water that forms a 1-km headland at the surface in Puget Sound, Washington. The form drag per unit length of the ridge reached 1 × 104 N m−1 during peak flood tides. The tidally averaged power removed from the tidal currents by form drag was 0.2 W m−2, which is 30 times larger than power losses to friction. Form drag is best parameterized by a linear wave drag law as opposed to a bluff body drag law because the flow is stratified and both internal waves and eddies are generated on the sloping topography. Maximum turbulent kinetic energy dissipation rates of 5 × 10−5 W kg−1 were measured with a microstructure profiler and are estimated to account for 25%–50% of energy lost from the tides. This study is among the first to measure form drag directly using bottom pressure sensors. The measurement and analysis techniques presented here are suitable for periodically reversing flows because they require the removal of a time-mean signal. The advantage of this technique is that it delivers a continuous record of form drag and is much less ship intensive compared to previous methods for estimation of the bottom pressure field.
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Lee, Jeffrey S., and Gerald B. Cleaver. "Relativistic drag and emission radiation pressures in an isotropic photonic gas." Modern Physics Letters A 31, no. 19 (2016): 1650118. http://dx.doi.org/10.1142/s0217732316501182.
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By invoking the relativistic spectral radiance, as derived by Lee and Cleaver,1 the drag radiation pressure of a relativistic planar surface moving through an isotropic radiation field, with which it is in thermal equilibrium, is determined in inertial and non-inertial frames. The forward- and backward-directed emission radiation pressures are also derived and compared. A fleeting (inertial frames) or ongoing (some non-inertial frames) Carnot cycle is shown to exist as a result of an intra-surfaces temperature gradient. The drag radiation pressure on an object with an arbitrary frontal geometry is also described.
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Song, XiaoWen, and MingXiao Zhang. "Turbulent Drag Reduction Characteristics of Bionic Nonsmooth Surfaces with Jets." Applied Sciences 9, no. 23 (2019): 5070. http://dx.doi.org/10.3390/app9235070.
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Aiming at aerodynamic drag reduction for transportation systems, a new active surface is proposed that combines a bionic nonsmooth surface with a jet. Simulations were performed in the computational fluid dynamics software STAR-CCM+ to investigate the flow characteristics and drag reduction efficiency. The SST K-Omega model was used to enclose the equations. The simulation results showed that when the active surface simultaneously reduced the skin friction and overcame the sharp increase of pressure drag caused by a common nonsmooth surface, the total net drag decreased. The maximum drag reduction ratio reached 19.35% when the jet velocity was 11 m/s. Analyses of the turbulent kinetic energy, pressure distribution, and velocity profile variations showed that the active surface reduced the peak pressure on the windward side of the nonsmooth unit cell, thereby reducing the total pressure drag. Moreover, the recirculation formed in the unit cell transformed the fluid–wall sliding friction into fluid–fluid rolling friction like a rolling bearing, thereby reducing the skin friction. This study provides a new efficient way for turbulent drag reduction to work.
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Cui, Hongjiang, Guanxin Chen, Ying Guan, and Wu Deng. "Study on Aerodynamic Drag Reduction at Tail of 400 km/h EMU with Air Suction-Blowing Combination." Machines 11, no. 2 (2023): 222. http://dx.doi.org/10.3390/machines11020222.
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In order to further reduce the aerodynamic drag of High-speed Electric Multiple Units (EMU), an active flow control drag reduction method combining air suction and blowing is proposed at the rear of the EMU train. A numerical calculation method based on realizable k-ε is used to investigate the aerodynamic drag characteristics of a three-car EMU with a speed of 400 km/h. The influence of different suction-blowing mass flow rates, the position and number of suction and blowing ports on the aerodynamic drag and surface pressure of the EMU tail are analyzed. The results demonstrate that suction and blowing at the tail reduce the pressure drag of EMU. And with the growth of air suction-blowing mass flow rate, the aerodynamic drag reduction rate of the tail car gradually increases, but the increment of drag reduction rate gradually decreases. Under the same mass flow rate of the suction and blowing, the closer the ports are to the upper and lower edges of the windscreen, the lower the pressure drag of the tail car is. At the same flow flux of air suction and blowing, the more the number of ports, the better the pressure drag reduction effect of the tail car. This study provides a reference for the next generation of EMU aerodynamic drag reduction and is of great significance for breaking through the limitations of traditional aerodynamic drag reduction.
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Hariyadi, Setyo. "An analysis on Aerodynamics Performance Simulation of NACA 23018 Airfoil Wings on Cant Angles." Journal of Energy, Mechanical, Material and Manufacturing Engineering 2, no. 1 (2017): 31. http://dx.doi.org/10.22219/jemmme.v2i1.4905.
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Winglet attached on the tip of aircraft wings to increase lift. Mainly, winglet used for increasing aerodynamic efficiency, it decreases induced drag caused by vortex on wings tip. The phenomenon of vortex is collision of high-pressured air below the wings meet the low-pressured air above it that cause turbulence. Induced drag may reach 40% of total drag during cruising, and 80-90% while take off. A procedure to decrease induced drag is using wing tip devices. It used on commercial aircrafts and the most frequently used is blended winglet. Numerical study conducted to examine the best aerodynamic performance of sub-sonic plane wings in angles of attack. Analysis on NACA 23018 airfoil wings with blended winglet on the tip was conducted. Freestream velocity of 40 m/s or Re = 1 × 106, and angle of attack (α) 0o, 5o, 10o, and 15o are used. Evaluation for parameter includes coefficient pressure (Cp), velocity profile, lift, drag, and ratio CL/CD. Obtained contour are pressure contour, velocity, and vorticity. In view of all this, there is increasing performance of aerodynamic with CL/CD ratio of wings with blended winglet and plain wing. Reaching current angle of attack, the function of winglet is gradually decrease.
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Gilotte, Philippe, Iraj Mortazavi, Alfonso Colon de Carvajal, Stephie Edwige, and Christian Navid Nayeri. "Aerodynamical characteristics of a reduced scale ground vehicle according to yaw angle variations." International Journal of Numerical Methods for Heat & Fluid Flow 32, no. 4 (2021): 1222–36. http://dx.doi.org/10.1108/hff-08-2021-0522.
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Purpose The purpose of this paper is to study pressure measurement correlations, as the location of the pressure sensors should enable to capture variation of the drag force depending on the yaw angle and some geometrical modifications. Design/methodology/approach The present aerodynamical study, performed on a reduced scale mock-up representing a sport utility vehicle, involves both numerical and experimental investigations. Experiments performed in a wind tunnel facility deal with drag and pressure measurements related to the side wind variation. The pressure sensor locations are deduced from wall streamlines computed from large eddy simulation results on the external surfaces of the mock-up. Findings After validation of the drag coefficient (Cd) values computed with an aerodynamic balance, measurements should only imply pressure tap mounted on the vehicle to perform real driving emission (RDE) tests. Originality/value Relation presented in this paper between pressure coefficients measured on a side sensor and the drag coefficient data must enable to better quantify the drag force contribution of a ground vehicle in RDE tests.
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GAO, Pengcheng, Qiaogao HUANG, Dong SONG, Guang PAN, and Yunlong MA. "Hydrodynamic performance study of manta ray gliding in groups." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 41, no. 3 (2023): 595–600. http://dx.doi.org/10.1051/jnwpu/20234130595.
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To investigate the effect of group gliding formation on the hydrodynamic performance of manta rays, numerical simulations were used to investigate the drag, the lift and pressure distribution of multiple manta rays in tandem, triangular and diamond-shaped arrangements. The simulation results show that the leader manta ray at the head of the group always suffers the least drag, and in most cases, the companion manta ray at the tail of the group suffers the most drag. The pressure distribution in the flow field shows that the drag reduction effect mainly comes from the distribution of high pressure and low pressure zones among the individual rays in the cluster, the high pressure zone is beneficial to the manta rays at the front of the group, and under certain circumstances, the presence of low pressure zone generates forward suction to reduce the drag of the manta rays at the end of the group. It is found that when manta rays glide in "two in front and one at the back", four-body diamond, six-body tandem and six-body diamond arrangement, the average drag of the system can be reduced, which provides theoretical guidance for the formation of bionic vehicle groups.
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Pierce, F. J., and S. K. Nath. "Interference Drag of a Turbulent Junction Vortex." Journal of Fluids Engineering 112, no. 4 (1990): 441–46. http://dx.doi.org/10.1115/1.2909423.
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The interference drag identified with the junction of a streamlined cylindrical body and a flat plate was investigated. The junction drag was calculated from a set of detailed, self consistent, high quality data using a control volume approach. The drag for the isolated flat plate and streamlined cylinder making up the junction was calculated using boundary-layer solvers together with surface pressure measurements. For the particular and relatively thick body under consideration, the results show a significant increase in drag due to the junction. These and other available results indicate that the interference drag has a systematic dependence on the thickness to chord ratio. The junction vortex wake increases the downstream flat plate drag significantly. Because of this effect, a unique value for the drag force, drag coefficient, or induced drag coefficient for a junction vortex flow would require that the geometry be specified in detail. The induced drag and the total pressure losses identified with the junction are also reported.
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SHINTANI, Mitsuhiro, and Yoshimichi HAGIWARA. "Pressure drag and friction drag for truncated pyramids in a turbulent open channel flow." Journal of Fluid Science and Technology 14, no. 1 (2019): JFST0001. http://dx.doi.org/10.1299/jfst.2019jfst0001.
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Wang, Xuanquan, Suwei Xiao, Xinchun Wang, and Debo Qi. "Numerical Simulation and Analysis of Added Mass for the Underwater Variable Speed Motion of Small Objects." Journal of Marine Science and Engineering 12, no. 4 (2024): 686. http://dx.doi.org/10.3390/jmse12040686.
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Unlike uniform motion, when an object moves underwater with variable speed, it experiences additional resistance from the water, commonly referred to as added mass force. At present, several methods exist to solve this force, including theoretical, experimental, and simulation approaches. This paper addresses the challenge of determining the added mass force for irregularly shaped small objects undergoing variable speed motion underwater, proposing a method to obtain the added mass force through numerical simulation. It employs regression analysis and parameter separation analysis to solve the added mass force, added mass, viscous drag coefficient, and pressure drag coefficient. The results indicate that an added mass force exists during both the acceleration and deceleration of the object, with little difference between them. Under the same velocity conditions, significant differences exist in pressure drag forces, while differences in viscous drag forces are not significant. This suggests that the primary source of added mass force is pressure drag, with viscous drag having little effect on it. During acceleration, the surrounding fluid accelerates with the object, increasing the pressure drag with a high-pressure area concentrating at the object’s front, forming an added mass force that is directed backward. By contrast, during deceleration, the fluid at the object’s front tends to detach, and the fluid at the rear rushes forward, leading to a smaller high-pressure area at the front and a larger one at the rear, reducing the pressure drag and forming an added mass force that is directed forward. By comparing the added mass of a standard ellipsoid obtained from numerical simulation with theoretical values, the regression analysis method is proven to be highly accurate and entirely applicable for solving the added mass of underwater vehicles.
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Zhou, Zhiwei, Chao Xia, Xizhuang Shan, and Zhigang Yang. "Numerical Study on the Aerodynamics of the Evacuated Tube Transportation System from Subsonic to Supersonic." Energies 15, no. 9 (2022): 3098. http://dx.doi.org/10.3390/en15093098.
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In this study, the aerodynamic characteristics of the three-dimensional evacuated tube transportation (ETT) system based on the Reynolds-averaged Navier–Stokes κ−ω shear-stress transport turbulent model were investigated. The effects of two key parameters on the drag and flow topology of the ETT system, namely the travelling speed and ambient pressure in the tube, were studied. Compared with trains in the atmospheric environment without the tube (i.e., the open system), the ETT system shows considerable drag reduction with suitable operating parameters in the tube, particularly at a higher travelling speed range. The drag varying with the speed from subsonic to supersonic, shows various change trends at different speeds because of their distinct flow structures. The higher pressure in front of train head was observed to be reduced by choking, and a low pressure in the wake by expansion waves led to rapid increase in the drag and drag coefficient. The relationship between the drag and operating pressure was observed to be approximately linear for both the subsonic and supersonic speeds.
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Hu, Xing Jun, Lei Liao, Xiu Cheng Li, et al. "Research on Automobile Aerodynamic Drag Reduction Based on Isobaric Surface of a Blunt Body." Applied Mechanics and Materials 328 (June 2013): 634–38. http://dx.doi.org/10.4028/www.scientific.net/amm.328.634.
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This paper focuses on a new method of aerodynamic drag reduction. In this paper numerical simulation method is adopted to investigate the relationship between the aerodynamic drag characteristics of a blunt body and the distribution of total pressure around the body. The study shows that when the shape of a blunt body is modified to be close to its isobaric surface, the pressure drag of the body can be reduced largely while the viscous drag increases slightly, and the summary of the drag gets lower as a result. This conclusion will have profound guiding significance in the aerodynamic shape designing and the aerodynamic drag reduction of an automobile.
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Nie, You, Ding Weng, and Jiadao Wang. "Underwater Drag Reduction Failure of Superhydrophobic Surface Caused by Adhering Spherical Air Bubbles." Journal of Marine Science and Engineering 12, no. 12 (2024): 2170. http://dx.doi.org/10.3390/jmse12122170.
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Underwater drag reduction using superhydrophobic surfaces is a promising method due to its simplicity and low energy consumption. However, most attempts to obtain drag reduction using superhydrophobic surfaces have failed. Explanations such as air layer or air bubble vanishment and surface roughness are proposed in the existing works. In this work, the drag increase caused by spherical air bubbles adhering to the superhydrophobic surface is reported, and the drag increase mechanism is revealed by numerical simulation. In the water tunnel and towing tank experiment, we found that the experimental samples exhibited drag increase around a specific velocity, and the recorded optical images showed that the superhydrophobic surfaces were adhered by spherical air bubbles. Through numerical simulation, we found that the spherical air bubbles not only reduced the frictional drag but also introduced pressure drag. The drag increase was produced when the introduced pressure drag exceeded the reduced frictional drag. This work might be helpful for the drag reduction application of the superhydrophobic surface.
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Arnott, A. D., L. Bernstein, and D. G. Petty. "A note on the pressure drag of a forward-swept-wing-plate junction." Aeronautical Journal 100, no. 997 (1996): 281–84. http://dx.doi.org/10.1017/s0001924000028918.
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SummaryThe forces due to normal pressure have been measured in the region of the junction between a rear-loaded wing swept forward at 28°, and a flat plate on which a turbulent boundary layer had developed. The Reynolds number was 1·03 × 106, based on the streamwise wing-chord of 500 mm. At low incidences, 0° < α ≤ 6°, the local pressure drag coefficients were found to be negativeaway from the junction, and the interaction with the junction was found to be favourable;that is the pressure drag coefficient became more negative as the junction was approached. At α = −3° the pressure drag coefficient changed from a positive value away from the junction to a negative value close to the plate. These results contrast with those for a swept-back wing-plate interaction, which has been reported as being unfavourable so far as the pressure drag was concerned. At 6° incidence, the interaction remained favourable but there was evidence of root stall beginning. At an incidence of 9°, root stall was much more marked and the positive pressure drag coefficient increased as the junction was approached.
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Sebben, Simone, Lennert Sterken, and Thies Wölken. "Characterization of the rear wake of a SUV with extensions and without extensions." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 231, no. 9 (2016): 1294–302. http://dx.doi.org/10.1177/0954407016678016.
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Passenger vehicles are considered to be bluff bodies, and therefore their total aerodynamic resistance is dominated by the pressure drag, which is basically the difference between the stagnation pressure at the front and the pressure at the base. In particular, the base wake of a vehicle has a significant influence on the total drag, and the ways to reduce and to control the drag have been the subject of numerous investigations. The present work focuses on the identification and analysis of unsteady-flow structures acting on the base wake of a sport utility vehicle with rear-end extensions and without rear-end extensions. Tapered extensions have proved to be an effective way to reduce the drag since they act as a truncated boat-tailing device which improves the pressure recovery zone and reduces the wake size. In this investigation, wind tunnel experiments and computational fluid dynamics were used to study the forces acting on the vehicle and the non-stationary behaviour of the rear wake flow. For analysis of the unsteady base pressures, a data-structure-sensitive filtering approach based on empirical mode decomposition in combination with fast Fourier transform and proper orthogonal decomposition was used. The numerical results and the experimental results complement each other well, and both revealed an antisymmetric mode in the transverse plane related to a flapping of the wake at a Strouhal number of around 0.23. Furthermore, a pumping effect, which is a main contributor to the drag, was observed at Strouhal values of between 0.04 and 0.07. This is in good agreement with the results from the research on more simplified model shapes. The rear extensions proved to be a productive way to reduce the drag coefficient and the magnitude of the wake flapping for the yaw angles investigated.
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Viswanath, P. R., and G. Rajendra. "Sting corrections to zero-lift drag of axisymmetric bodies in transonic flow." Aeronautical Journal 94, no. 938 (1990): 279–88. http://dx.doi.org/10.1017/s0001924000023095.
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AbstractExperiments at transonic speeds have been performed on several boat-tailed afterbodies and sting combinations with a view to assessing sting corrections to the measured afterbody drag at transonic speeds. Measurements made included afterbody total drag and base pressure in the Mach number range of 0.6-1.0 and Reynolds number range of 8-9.5 x 106. Correlations of base pressure and boat-tail pressure drag for the sting diameter and flare effects have been proposed using dimensional arguments. The correlations provide quick and reliable estimates for corrections that can be applied to the measured zero-lift drag of axisymmetric bodies with either contoured or conical boat-tailing.
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Zhang, Yufei, Chongyang Yan, and Haixin Chen. "An Inverse Design Method for Airfoils Based on Pressure Gradient Distribution." Energies 13, no. 13 (2020): 3400. http://dx.doi.org/10.3390/en13133400.
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An airfoil inverse design method is proposed by using the pressure gradient distribution as the design target. The adjoint method is used to compute the derivatives of the design target. A combination of the weighted drag coefficient and the target dimensionless pressure gradient is applied as the optimization objective, while the lift coefficient is considered as a constraint. The advantage of this method is that the designer can sketch a rough expectation of the pressure distribution pattern rather than a precise pressure coefficient under a certain lift coefficient and Mach number, which can greatly reduce the design iteration in the initial stage of the design process. Multiple solutions can be obtained under different objective weights. The feasibility of the method is validated by a supercritical airfoil and a supercritical natural laminar flow airfoil, which are designed based on the target pressure gradients on the airfoils. Eight supercritical airfoils are designed under different upper surface pressure gradients. The drag creep and drag divergence characteristics of the airfoils are numerically tested. The shockfree airfoil demonstrates poor performance because of a high suction peak and the double-shock phenomenon. The adverse pressure gradient on the upper surface before the shockwave needs to be less than 0.2 to maintain both good drag creep and drag divergence characteristics.
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Todd, D. B. "Drag and Pressure Flow in Twin Screw Extruders." International Polymer Processing 6, no. 2 (1991): 143–47. http://dx.doi.org/10.3139/217.910143.
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Grinstein, F. F., J. P. Boris, and O. M. Griffin. "Passive pressure-drag control in a plane wake." AIAA Journal 29, no. 9 (1991): 1436–42. http://dx.doi.org/10.2514/3.10757.
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Jung, Thomas, and Peter B. Rhines. "Greenland’s Pressure Drag and the Atlantic Storm Track." Journal of the Atmospheric Sciences 64, no. 11 (2007): 4004–30. http://dx.doi.org/10.1175/2007jas2216.1.
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Abstract Some effects of Greenland on the Northern Hemisphere wintertime circulation are discussed. Inviscid pressure drag on Greenland’s slopes, calculated from reanalysis data, is related to circulation patterns. Greenland lies north of the core of the tropospheric westerly winds. Yet strong standing waves, which extend well into the stratosphere, produce a trough/ridge system with jet stream lying close to Greenland, mean Icelandic low in its wake, and storm track that interacts strongly with its topography. In the lower troposphere, dynamic height anomalies associated with strongly easterly pressure drag on the atmosphere are quite localized in space and relatively short-lived compared to upper levels, yet they involve a hemispheric-scale dislocation of the stratospheric polar vortex. It is a two-scale problem, however; the high-pass time-filtered part of the height field, responsible for 73% of the pressure drag, is quite different, and expresses propagating cyclonic development in the Atlantic storm track. Eliassen–Palm flux (EP flux) analysis shows that the atmospheric response is (counterintuitively) an acceleration of the westerly winds. The hemispheric influence is consistent with the model results of Junge et al. suggesting that Greenland affects the stationary waves in winter. This discussion shows that Greenland is not a simple “stirring rod” in the westerly circulation, yet involvement of Greenland’s topography with the shape, form, and intensity of the storm track is strong. Interaction of traveling storms, the jet stream, and the orographic wake frequently leads to increase of the lateral scale such that cyclonic system expands to the size of Greenland itself (∼2500 km). Using the global ECMWF general circulation model, the authors explore the effect of model resolution on these circulations. Statistically, in two case studies, and in higher-resolution global models at TL255 to TL799 resolution, intense tip jet, hydraulic downslope jet, and gravity wave radiation appear in strong flow events, in accord with the work of Doyle and Shapiro. Three-dimensional particle trajectories and vorticity maps show the nature and intensity of the summit-gap flow. Cyclonic systems in the lee of Greenland are strongly affected by the downslope jet. Penetration of the Arctic Basin by cyclonic systems arises from this source region, and the amplitude of the pressure drag is enhanced at high resolution. At the higher resolutions, storm-track analysis verifies the splitting of the storm track by Greenland with a substantial minority of storms moving northward through Baffin Bay. Finally, analysis of 20 winters of 40-yr ECMWF Re-Analysis (ERA-40) reforecasts shows little evidence that negative pressure-drag events are followed by anomalously large forecast errors over Europe, throughout the forecast. Forecast skill for the pressure drag is surprisingly good, with a correlation of 0.65 at 144 h.
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Winiecki, T., J. F. McCann, and C. S. Adams. "Pressure Drag in Linear and Nonlinear Quantum Fluids." Physical Review Letters 82, no. 26 (1999): 5186–89. http://dx.doi.org/10.1103/physrevlett.82.5186.
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Krupitsky, Alexander, and Mark A. Cane. "On topographic pressure drag in a zonal channel." Journal of Marine Research 52, no. 1 (1994): 1–23. http://dx.doi.org/10.1357/0022240943076740.
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Sokhan, V. P., N. Quirke, and J. Greenwood. "Viscous drag forces in gas operated pressure balances." Molecular Simulation 31, no. 6-7 (2005): 535–42. http://dx.doi.org/10.1080/08927020500134318.
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Warner, Sally J., and Parker MacCready. "Dissecting the Pressure Field in Tidal Flow past a Headland: When Is Form Drag “Real”?" Journal of Physical Oceanography 39, no. 11 (2009): 2971–84. http://dx.doi.org/10.1175/2009jpo4173.1.
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Abstract In the few previous measurements of topographic form drag in the ocean, drag that is much larger than a typical bluff body drag estimate has been consistently found. In this work, theory combined with a numerical model of tidal flow around a headland in a channel gives insight into the mechanisms that create form drag in oscillating flow situations. The total form drag is divided into two parts: the inertial drag, which is derived from a local potential flow solution, and the separation drag, which accounts for flow features such as eddies. The inertial drag can have a large magnitude, yet it cannot do work on the flow because its phase is in quadrature with the velocity. The separation drag has a magnitude that is nearly equal to the bluff body drag and accounts for all of the energy removed from the flow by the topography. In addition, the dependence of the form drag on the tidal excursion distance and the aspect ratio of the headlands were determined with a series of numerical experiments. This theory explains why form drag can be so large in the ocean, and it provides a method for separating the pressure field into the parts that can and cannot extract energy from the flow.
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Zhong, Chuxiang, Li Cai, Yibin Mao, Kaiwen Yang, Xiaokang Yang, and Dianlong Yu. "Design of drag reduction and water pressure resistant skin layer of underwater vehicle based on mechanical metamaterials." Journal of Physics: Conference Series 2951, no. 1 (2025): 012122. https://doi.org/10.1088/1742-6596/2951/1/012122.
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Abstract Developing high-speed and large working depth underwater vehicles has gradually become a hot topic. Various drag-reduction skins and water pressure-resistant structures have been proposed to reduce surface resistance interference and increase the working water depth. Mechanical metamaterials can exhibit extraordinary static mechanical and quasi-static mechanical properties. It provides possibilities for achieving excellent static water pressure resistance and drag reduction simultaneously. This paper proposed an underwater elastic skin based on metamaterials and drag-reducing grooves. A composite functional skin was obtained by combining the negative Poisson’s ratio design of metamaterials with the V-groove drag reduction design. Analysis based on the COMSOL finite element simulation shows that lower flow resistance during high-speed and low-speed navigation and stronger pressure resistance can be achieved simultaneously. By comparing different drag reduction models, the drag reduction characteristics of the composite skin are analyzed. The results provide new ideas for the design of thin-layer multifunctional integrated underwater skins for UUV.
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Zhang, B. F., K. Liu, Y. Zhou, S. To, and J. Y. Tu. "Active drag reduction of a high-drag Ahmed body based on steady blowing." Journal of Fluid Mechanics 856 (October 4, 2018): 351–96. http://dx.doi.org/10.1017/jfm.2018.703.
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Active drag reduction of an Ahmed body with a slant angle of $25^{\circ }$, corresponding to the high-drag regime, has been experimentally investigated at Reynolds number $Re=1.7\times 10^{5}$, based on the square root of the model cross-sectional area. Four individual actuations, produced by steady blowing, are applied separately around the edges of the rear window and vertical base, producing a drag reduction of up to 6–14 %. However, the combination of the individual actuations results in a drag reduction 29 %, higher than any previous drag reductions achieved experimentally and very close to the target (30 %) set by automotive industries. Extensive flow measurements are performed, with and without control, using force balance, pressure scanner, hot-wire, flow visualization and particle image velocimetry techniques. A marked change in the flow structure is captured in the wake of the body under control, including the flow separation bubbles, over the rear window or behind the vertical base, and the pair of C-pillar vortices at the two side edges of the rear window. The change is linked to the pressure rise on the slanted surface and the base. The mechanisms behind the effective control are proposed. The control efficiency is also estimated.
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Tiwari, Jayesh Anil. "Hypersonic Flow past LD-Haack Series, Parabolic Series, Power Series Nose Cone: A Comparative Study." International Journal for Research in Applied Science and Engineering Technology 12, no. 10 (2024): 191–31. http://dx.doi.org/10.22214/ijraset.2024.64487.
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This research paper presents a detailed aerodynamic analysis of three rocket nose cone designs—LD-Haack, Parabolic, and Power Series—under hypersonic conditions ranging from Mach 5 to Mach 12. Using advanced Computational Fluid Dynamics (CFD) simulations in ANSYS Fluent, the study focuses on key aerodynamic parameters, including drag force, drag coefficient, velocity, pressure, and temperature distributions. The results indicate that the Parabolic Nose Cone offers the most favorable aerodynamic performance, with the lowest drag force and drag coefficient across all Mach numbers. This superior performance can be attributed to its ability to streamline airflow and minimize boundary layer separation, effectively reducing pressure drag and limiting the onset of turbulent wake regions. In contrast, the LD-Haack Series Nose Cone, though designed to minimize wave drag at supersonic speeds, shows moderate drag at hypersonic velocities due to its less optimal control of boundary layer behavior. The Power Series Nose Cone, despite its highly tapered shape, experiences the highest drag. This is largely caused by increased flow separation and turbulent wake generation, which exacerbate pressure drag, particularly at higher Mach numbers. These findings highlight the critical influence of nose cone geometry on aerodynamic efficiency and emphasize the importance of optimizing designs for hypersonic applications. This study provides valuable insights for aerospace engineers seeking to reduce drag and improve performance in high-speed flight scenarios.
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Imam, Muhammad, Ade Sunardi, and Mohamad Zaenudin. "Analisis Ketahanan Rangka Stasiun Pengisian Kendaraan Listrik Berbasis Panel Surya Portabel Terhadap Laju Angin." Integrated Mechanical Engineering Journal 1, no. 1 (2024): 19–29. http://dx.doi.org/10.56904/imejour.v1i1.3.
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High wind velocity can induce external pressures and loads on the structural framework of an Electric Vehicle Charging Station (EVCS), jeopardizing the overall stability and structural integrity of the framework. The objective of this research is to ascertain the magnitude of aerodynamic drag force and the maximum pressure values on the surface of the EVCS framework, with respect to variations in wind velocity. The methodology employed in this study involves Computational Fluid Dynamics (CFD) simulations utilizing the Solidworks Flow Simulation. Three wind velocity scenarios were considered: 3 km/h, 6 km/h, and 9 km/h, allowing for the observation of airflow acceleration phenomena, aerodynamic drag force values, and peak pressure distributions on the EVCS framework's surface. Research findings reveal that the aerodynamic drag force at a wind velocity of 3 km/h measures 22,34 N, escalating to 90,42 N at 6 km/h wind velocity, and reaching 202,7 N at 9 km/h wind velocity. Furthermore, the highest-pressure value at a wind velocity of 3 km/h is 101325,45 Pa. As the wind velocity increases to 6 km/h, the maximum pressure value rises to 101338,18 Pa. Under the condition of the highest input wind velocity, i.e., 9 km/h, the peak pressure reaches 101353,46 Pa.
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Sekhar, T. V. S., R. Sivakumar, and T. V. R. Ravi Kumar. "Drag and pressure fields for the MHD flow around a circular cylinder at intermediate Reynolds numbers." Journal of Applied Mathematics 2005, no. 3 (2005): 183–203. http://dx.doi.org/10.1155/jam.2005.183.
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Steady incompressible flow around a circular cylinder in an external magnetic field that is aligned with fluid flow direction is studied forRe(Reynolds number) up to 40 and the interaction parameter in the range0≤N≤15(or0≤M≤30), whereMis the Hartmann number related toNby the relationM=2NRe, using finite difference method. The pressure-Poisson equation is solved to find pressure fields in the flow region. The multigrid method with defect correction technique is used to achieve the second-order accurate solution of complete nonlinear Navier-Stokes equations. It is found that the boundary layer separation at rear stagnation point forRe=10is suppressed completely whenN<1and it started growing again whenN≥9. ForRe=20and 40, the suppression is not complete and in addition to that the rear separation bubble started increasing whenN≥3. The drag coefficient decreases for low values ofN(<0.1)and then increases with increase ofN. The pressure drag coefficient, total drag coefficient, and pressure at rear stagnation point vary withN. It is also found that the upstream and downstream pressures on the surface of the cylinder increase for low values ofN(<0.1)and rear pressure inversion occurs with further increase ofN. These results are in agreement with experimental findings.
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Jiang, Hai Bo, Yan Ru Li, and Zhong Qing Cheng. "Relations of Lift and Drag Coefficients of Flow around Flat Plate." Applied Mechanics and Materials 518 (February 2014): 161–64. http://dx.doi.org/10.4028/www.scientific.net/amm.518.161.
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In this paper, when Reynolds number is within the range of 10000 to 1000000, the horizontal component of the total pressure of flow around flat plate at high angle of attack was regarded as lift of high angle of attack, and the vertical component was regarded as drag of high angle of attack. The horizontal component of total pressure at small angle of attack was regarded as shape drag, and the total drag coefficient at small angle of attack was considered to the sum of the shape drag and frictional drag at zero angle of attack. For the two states of large and small angle of attack, the application scopes of the formulas of lift and drag coefficients were given. Final, the relations of lift and drag coefficients were obtained by eliminating all angles of attack. Research results show that lift - drag curve of small angles of attack is parabola, and the lift - drag curve of high angles of attack is circle.
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Liang, Xifeng, Zhangjun Luo, Xiaobai Li, Xiaohui Xiong, and Xin Zhang. "Drag reduction of high-speed trains via low-density gas injection." AIP Advances 12, no. 6 (2022): 065115. http://dx.doi.org/10.1063/5.0089141.
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Aerodynamic drag reduction is crucial for the development of high-speed trains. This study considers the principle of supercavitation torpedo drag reduction and conducts wind tunnel tests and improved delayed detached eddy simulation numerical simulations to develop a drag reduction technique using low-density gas injection on the surface of a high-speed train. Models for jetting gases with different densities on the surface of the high-speed train were employed, and the aerodynamic drag, frictional resistance, pressure resistance, and flow field structure were compared and analyzed. The results demonstrated that jetting of low-density gas reduced the drag of the train, whereas air and high-density gas increased the drag. The jetting gas reduced the frictional resistance of the train to a certain extent and low-density gas injection significantly reduced the frictional resistance. However, the pressure resistance coefficient increased with an increase in the density of the jetting gas, resulting in increased drag. The density of the gas medium in the boundary layer significantly decreased when low-density gas was jetted and the effect of reducing the friction resistance was superior. The pressure resistance between the front and rear of the jet port increased with an increase in the gas density, thereby increasing the drag on the train.
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Li, Hongbo, Jiancheng Yu, Zhier Chen, Kai Ren, and Zhiduo Tan. "Adjustability and Stability of Flow Control by Periodic Forcing: A Numerical Investigation." Journal of Marine Science and Engineering 12, no. 9 (2024): 1613. http://dx.doi.org/10.3390/jmse12091613.
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The efficient and stable application of periodic forcing for drag-reduction can help underwater vehicles operate at high speed for long durations and improve their energy-utilization efficiency. This study considers flow control around a body-of-revolution model subjected to periodic blowing or suction through annular slots. The focus is on the boundary-layer structure, properties, and drag of the control fluid under a wide range of body variables (size, free-flow velocity, slot area, and blowing/suction velocity) and control parameters (normalized periodic-forcing amplitude and relative slot sizes). Body variables differ in their effects on the drag-reduction rate, with the surface pressure pushing the model vehicle when S and v are higher than S0 and v0. In particular, the lowest pressure drag was −26.4 N with v increasing, and the maximum drag-reduction rate of total drag exceeded 135%. At a fixed Reynolds number, increasing the values of the control parameters leads to larger-scale unstable vortex rings downstream from the slots; the surface-velocity gradient is reduced, effectively lowering the drag. A simple model relating the periodic fluctuation of pressure drag to the body variables is developed through quantitative analysis and used to determine navigational stability.