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Dissertations / Theses on the topic 'Fluid- and Aerodynamics'

Author: Grafiati

Published: 4 June 2021

Last updated: 30 July 2024

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1

Barman, Emelie. "Aerodynamics of Flutter." Thesis, KTH, Mekanik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-34152.

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The unsteady ow around an aerofoil placed in a uniform ow stream with an angle of attack is investigated, under the assumption of inviscid, incompressible, two-dimensional flow. In particular, a function of the velocity jump over the wake is achieved, where this function depends on the horizontal displacement and time. The aerofoil geometry is represented by two arbitrary functions, one for the upper and one for the lower side of the aerofoil. These functions are dependent on time, hence the aerofoil can perform oscillating movement, which is the case when subjected to utter. The governing equations for the ow are the Euler equations. By assuming thin aerofoil, small angle of attack and that the perturbation of the wake is small, the problem is linearised. It is shown that the linearised Euler equations can be rewritten as the Cauchy-Riemann equations, and an analytic function exists where its real part is the horizontal velocity component and its imaginary part is the vertical velocity component with opposite sign. The ow eld is then investigated in the complex plane by making an appropriate branch cut removing all discontinuities, and with restrictions on the analytic function such that the kinematic and boundary conditions are satis ed. By using Cauchy's integral formula an expression for the anti-symmetric part of the analytic function is achieved. A general expression for the velocity jump over the wake is obtained, which is applied to the speci c case of harmonic oscillations for a symmetric aerofoil. In the end three types of utter is investigated; twisting oscillations around the centre of stiness, vertical oscillation, and aileron flutter.

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2

Horton, F. G. "Aerodynamics and heat transfer of turbine blading." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375214.

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3

Peters, Brett. "On Accelerating Road Vehicle Aerodynamics." Thesis, The University of North Carolina at Charlotte, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10791882.

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Road vehicle aerodynamics are primarily focused on developing and modeling performance at steady-state conditions, although this does not fully encompass the entire operating envelope. Considerable vehicle acceleration and deceleration occurs during operation, either because of driver input or from transient weather phenomenon such as wind gusting. With this considered, high performance road vehicles experience body acceleration rates well beyond ±1G to navigate courses during efficient transition in and out of corners, accelerating from maximum straight-line speed to manageable cornering speeds, and then back to maximum straight-line speed. This dissertation aims to answer if longitudinal acceleration is important for road vehicle aerodynamics with the use of transient Computational Fluid Dynamics (CFD) to develop a method for obtaining ensemble averages of forces and flow field variables. This method was developed on a simplified bluff body, a channel mounted square cylinder, achieving acceleration through periodic forcing of far field velocity conditions. Then, the method was applied to an open-source road vehicle geometry, the DrivAer model, and a high performance model which was created for this dissertation, the DrivAer-GrandTouringRacing (GTR) variant, as a test model that generates considerable downforce with low ground proximity. Each test body experienced drag force variations greater than ±10% at the tested velocities and acceleration rates with considerable variations to flow field distributions. Finally, an empirical formulation was used to obtain non-dimensional coefficients for each body from their simulated force data, allowing for force comparison between geometries and modeling of aerodynamic force response to accelerating vehicle conditions.

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4

Melius, Matthew Scott. "Mechanisms and Identification of Unsteady Separation Development and Remediation." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4064.

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Unsteady flow separation represents a highly complex and important area of study within fluid mechanics. The extent of separation and specific time scales over which it occurs are not fully understood and has significant consequences in numerous industrial applications such as helicopters, jet engines, hydroelectric turbines and wind turbines. A direct consequence of unsteady separation is the erratic movement of the separation point which causes highly dynamic and unpredictable loads on an airfoil. Current computational models underestimate the aerodynamic loads due to the inaccurate prediction of the emergence and severity of unsteady flow separation especially in response to a sudden change in the effective angle of attack. To capture the complex flow phenomena over wind turbine blades during stall development, a scaled three-dimensional non-rotating blade model is designed to be dynamically similar to a rotating full-scale NREL 5MW wind turbine blade. A time-resolved particle image velocimetry (PIV) investigation of flow behavior during the stall cycle examines the processes of stall development and flow reattachment. The flow fields are examined through the application of Eulerian techniques such as proper orthogonal decomposition and empirical mode decomposition to capture unsteady separation characteristics within the flow field. Then, for a higher order description, coherent structures such as vortices and material lines are resolved to fully characterize the flow during a full pitching cycle in a Lagrangian framework. The Eulerian and Lagrangian methods described in the present analysis is extended to investigate the spanwise characteristics within the root section of a three dimensional airfoil. Furthermore, statistical information of the separation point is pursued along four spanwise positions during two cases of unsteady separation. The results of the study describe a critical role of surface vorticity accumulation in unsteady separation and reattachment. Evaluation of the unsteady characteristics of the shear layer reveal evidence that the build-up and shedding of surface vorticity directly influence the dynamic changes in separation point. The quantitative characterization of surface vorticity and shear layer stability enables improved aerodynamic design, but also has broader implications on the larger discipline of unsteady fluid dynamics.

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5

Lejon, Marcus. "Aerodynamic Investigation of Air Inlets on Aircrafts with Application of Computational Fluid Dynamics." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-12820.

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Air inlets in some form are used on all commercial airliners today. The type of air inlet investigated in this report is a NACA inlet submerged into a surface. This surface is within this thesis a test section wall of a wind tunnel. The considered wind tunnel is TWG in Göttingen (Germany) that operates in transonic speeds. Submerged inlets have the main advantage of low aeroynamic drag from the inlet itself. The importance of reducing drag, and the attention given to this subject is increasing as fuel prices rise as well as public awareness of environmental impact by all of us. The outcome of this thesis contributes to the government-funded project ECOCENTS which deals with the design of innovative new aircraft cooling systems and the detailed flow analysis of these systems. This thesis was carried out at the company Airbus in Bremen, Germany. The main objective of this report was the evaluation of the ram pressure efficiency of four different ramp angles of a NACA inlet and the estimation of the drag caused by these geometries with the use of Computational Fluid Dynamics (CFD). The flow solver used was TAU, a Reynolds-Averaged Navier-Stokes (RANS) solver developed by the German Aerospace Center (DLR). The inlet consisted of one ramp section where the ramp angle was fixed at 7 degrees, and a second variable ramp section. The following different angles were investigated: 4, 7, 10 and 15 degrees. These configurations were evaluated at a velocity of Mach 0.8 and a Reynolds number of 10*10^6. The ramp angle of 7 degrees was evaluated at two additional velocities (Mach 0.73 and Mach 0.87) and at two additional Reynolds numbers (5*10^6 and 15*10^6) at Mach 0.8. The inlet efficiency outcome of this study was located between two other investigations. The results of this RANS computation predicted a higher total pressure at the inlet throat plane compared to a previous CFD investigation where a different RANS solver at the same geometry was used. In comparison to an estimation method mainly based on experimental data (ESDU method), the recent study showed a lower total pressure at the inlet throat plane. The aerodynamic drag that arised by the presence of the inlet system was calculated within this thesis to be higher than the outcome of the experimental data based (ESDU) method. The advantage of using a NACA type inlet was observed to be highly related to the ramp angle. Vortices are originated and develop along the edges of the intake ramp walls. These two vortices help to transport higher energy flow from the free stream into the inlet and therefore reduce the boundary layer thickness in the inlet region. For lower mass flows (0.10 - 0.20 kg/s) a ramp angle of 7 degrees was seen to be prefered in view of ram pressure efficiency. At a higher mass flow (0.25 kg/s) the 10 degrees ramp angle was prefered, followed by the 15 degrees ramp angle at the highest investigated mass flows (0.30 - 0.35 kg/s). In view of drag, the lowest ramp angle possible for a given mass flow was seen to be most advantagous. Future work on this subject will include simulation of an inlet in combination with a heat exchanger and a ram air outlet. This arrengement will be the same as in the investigation at the TWG test campaign and therefore comparable. The difference in outcome of the separate CFD analysis was discussed within this investigation but could not be completely cleared.

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6

Henderson, Jason. "Investigation of cavity flow aerodynamics using computational fluid dynamics." Thesis, University of Glasgow, 2001. http://theses.gla.ac.uk/3483/.

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Open cavity flow is that of most interest to researchers. The flow is typical to that found to exist in the bomb bay of the F-111 and is characterised by intense acoustic levels. A review of the work of previous experimental researchers is included for comparison with the findings of the present thesis. The flow physics indicate that a series of vortices travel downstream in the cavity and are driven by vorticity generated at the upstream lip of the cavity. When strengthened the downstream moving vortex influences the mass addition and expulsion at the trailing edge initiating a pressure wave which propagates upstream and sustains the process of completing the feedback lopp. These features are elucidated upon in the present thesis. The flow at Mach 0.85 and Mach 1.19 is analysed with only differences in the external stream being apparent for the higher Mach number case. The suppression of the acoustic environment is investigated by sloping the aft wall of the cavity. The results of the CFD study are used to examine why sloping of the aft cavity wall is successful. It is shown that the flow tends towards a steady state and the results are compared to the hypothesis of Heller and Bliss. This hypothesis is substantiated by the present simulations and in doing so the work demonstrates the ability of CFD to be used as a tool in conjunction with experimental methods to enhance the understanding of cavity flows. An area of cavity flows for which information is sparse is for the transitional cavity flows. A review of the literature shows that the 4 types of cavity flow exist at supersonic speeds and these are identified by the CFD. The results of the computational study are used to examine when the impingement and exit shocks, characteristic of closed cavity flow, collapse to form a single shock wave. This point is defined as L/Dcrit and occurs when the vertices of the separation and recompression wakes merge. It represents the boundary between transitional-closed flow and closed flow and the CFD predictions are compared to Prandtl-Meyer theory when investigating the position of L/Dcrit.

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7

Khorrami, Ahmad Farid. "Hypersonic aerodynamics on flat plates and thin aerofoils." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292584.

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8

Coverston, Joseph S. "Numerical Simulation of Flushing Deposits in Pipelines." FIU Digital Commons, 2019. https://digitalcommons.fiu.edu/etd/3951.

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The purpose of this research is to reduce the amount of waste generated in Department of Energy nuclear cleanup efforts currently underway. Due to the highly radioactive nature of the waste, any fluid that contacts the waste must then be treated and processed as waste. To minimize the fluids contaminated during flushing, this research aims to provide a basis for the flushing of High Level Waste (HLW) pipelines. Edgar Plastic Kaolin (EPK) with solid particles of a nominal diameter of 1 micron was used as a simulacrum for HLW. An Eulerian-Eulerian simulation built in StarCCM+ software, with a k-ω turbulence model, and a drag coefficient to connect the solid EPK phase with the liquid phase, was used to simulate the flushing of pipelines. Velocities from 3 ft/s to 10 ft/s were investigated to find the highest volumetric efficiency, and it was determined that 10 ft/s was the optimal flushing velocity.

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9

Sharpe, Jacob Andrew. "3D CFD Investigation of Low Pressure Turbine Aerodynamics." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1495872867696744.

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10

Menzies, Ryan D. D. "Investigation of S-shaped intake aerodynamics using computational fluid dynamics." Thesis, University of Glasgow, 2002. http://theses.gla.ac.uk/1440/.

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Flows in the s-shaped intake (Royal Aircraft Establishment intake model 2129-M2129) have been simulated and analysed using Computational Fluid Dynamics (CFD). Various flows have been simulated from steady through-flow for validation and verification, steady flows at a variety of angles of pitch and yaw, and the unsteady flow of surge wave propagation following the application of surge signatures at the engine face. Reynolds Averaged Navier-Stokes (RANS) simulations have been considered using the SA, k- ω and SST turbulence models where possible. The freestream Mach number was fixed at 0.21 and the Reynolds number based on the non-dimensional engine face diameter was 777,000 for all cases. The Glasgow flow solver PMB was used and second order accuracy was achieved in both space and time. Grid and time step convergence studies verified the numerical method, the grids being of the structured multi-block type. A comprehensive validation study was undertaken on the steady through-flow problem. Previously examined low and high mass flow cases were studied. It was found that the low mass flow results compared well with previous computational solutions. Problems however were encountered in the quantitative prediction of the secondary flow when compared with experiment however the SST model did quantitatively predict this. The high mass flow case proved more challenging. Solutions predicted two different flow regimes depending on the turbulence model used. It was found that the SST model provided a good matched with the primary set of experimental data. Confidence in this result was gained as it also performed well in the low mass flow case and also as it has shown previous improvements in the prediction of separation in flows with strong adverse pressure gradients.

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11

Hammargren, Kristoffer. "Aerodynamics Modeling of Sounding Rockets : A Computational Fluid Dynamics Study." Thesis, Luleå tekniska universitet, Strömningslära och experimentell mekanik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-70551.

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12

Yan, Zhimiao. "Modeling of Nonlinear Unsteady Aerodynamics, Dynamics and Fluid Structure Interactions." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/71824.

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We model different nonlinear systems, analyze their nonlinear aspects and discuss their applications. First, we present a semi-analytical, geometrically-exact, unsteady potential flow model is developed for airfoils undergoing large amplitude maneuvers. Towards this objective, the classical unsteady theory of Theodorsen is revisited by relaxing some of the major assumptions such as (1) flat wake, (2) small angle of attack, (3) small disturbances to the mean flow components, and (4) time-invariant free-stream. The kinematics of the wake vortices is simulated numerically while the wake and bound circulation distribution and, consequently, the associated pressure distribution are determined analytically. The steady and unsteady behaviors of the developed model are validated against experimental and computational results. The model is then used to determine the lift frequency response at different mean angles of attack. Second, we investigate the nonlinear characteristics of an autoparametric vibration system. This system consists of a base structure and a cantilever beam with a tip mass. The dynamic equations for the system are derived using the extended Hamilton's principle. The method of multiple scales is then used to analytically determine the stability and bifurcation of the system. The effects of the amplitude and frequency of the external force, the damping coefficient and frequency of the attached cantilever beam and the tip mass on the nonlinear responses of the system are determined. As an application, the concept of energy harvesting based on the autoparametric vibration system consisting of a base structure subjected to the external force and a cantilever beam with a tip mass is evaluated. Piezoelectric sheets are attached to the cantilever beam to convert the vibrations of the base structure into electrical energy. The coupled nonlinear distributed-parameter model is developed and analyzed. The effects of the electrical load resistance on the global frequency and damping ratio of the cantilever beam are analyzed by linearizion of the governing equations and perturbation method. Nonlinear analysis is performed to investigate the impacts of external force and load resistance on the response of the harvester. Finally, the concept of harvesting energy from ambient and galloping vibrations of a bluff body is investigated. A piezoelectric transducer is attached to the transverse degree of freedom of the body in order to convert the vibration energy to electrical power. A coupled nonlinear distributed-parameter model is developed that takes into consideration the galloping force and moment nonlinearities and the base excitation effects. The aerodynamic loads are modeled using the quasi-steady approximation. Linear analysis is performed to determine the effects of the electrical load resistance and wind speed on the global damping and frequency of the harvester as well as on the onset of instability. Then, nonlinear analysis is performed to investigate the impact of the base acceleration, wind speed, and electrical load resistance on the performance of the harvester and the associated nonlinear phenomena. Short- and open-circuit configurations for different wind speeds and base accelerations are assessed
Ph. D.

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13

Murad, Nurul Muiz. "Computational fluid dynamics (CFD) of vehicle aerodynamics and associated acoustics." Swinburne Research Bank, 2009. http://hdl.handle.net/1959.3/47824.

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Thesis (PhD) - Swinburne University of Technology, School of Engineering and Science, 2009.
A thesis submitted in accordance with the regulations for the degree of Doctor of Philosophy, School of Engineering and Science, Swinburne University of Technology, 2009. Typescript. Includes bibliographical references (p. 315-330)

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14

Baldovin, Brandon James. "Sweep and Taper Analysis of Surfboard Fins Using Computational Fluid Dynamics." DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/1983.

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The research presented here provides a basis for understanding the hydrodynamics of surfboard fin geometries. While there have been select studies on fins there has been little correlation to the shape of the fin and its corresponding hydrodynamic performance. This research analyzes how changing the planform shape of a surfboard fin effects its performance and flow field. This was done by isolating the taper and sweep distribution of a baseline geometry and varying each parameter individually whilst maintaining a constant span and surface area. The baseline surfboard fin was used as a template in Matlab to generate a set of x and y coordinates that defined the outline of the fin shape. These coordinates were then altered by changing either the sweep or taper distribution and resulted in new, unique planform shapes. The new shapes were used to generate 3D models with the NACA 0006 foil as the cross-section hydrofoil. After the geometry was modeled, each fin was meshed and simulated in CFD for incidence angles ranging from 0o to 20o and a fin Reynolds Number of 3.51x105. When the sweep distribution was changed, there was a direct correlation to vortex formation off the leading edge. Increasing the sweep generated a stronger vortex that persisted for higher angles of attack and resulted in higher moments but increased drag. Changing the taper distribution was not as influential. The tapered fin set showed similar flow fields and body forces to each other. Making a fin more rectangular had slight decreases in drag but made the shape more prone to separation.

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15

Terzi, Antonia. "A combination of computational fluid dynamic methods for formula-1 aerodynamic analysis." Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286545.

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16

Tuncer, Ismail H. "Unsteady aerodynamics of oscillating and rapidly pitched airfoils." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/12522.

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17

Guerra, Joel Tynan. "Investigating the Effect of an Upstream Spheroid on Tandem Hydrofoils." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1959.

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This thesis documents a series of three dimensional unsteady Reynolds Averaged Navier-Stokes CFD simulations used to investigate the inﬂuence of an upstream prolate spheroid body on tandem pitching hydrofoils. The model is validated by performing separate CFD simulations on the body and pitching hydrofoils and comparing results to existing experimental data. The simulations were run for a range of Strouhal numbers (0.2-0.5) and phase diﬀerences (0-π). Results were compared to identical simulations without an upstream body to determine how the body aﬀects thrust generation and the unsteady ﬂow ﬁeld. The combined time-averaged thrust increases with Strouhal number, and is highest when the foils pitch out of phase with each other. At intermediate phase diﬀerences between φ = 0 and φ = π the leading foil produces signiﬁcantly more thrust than the trailing foil, peaking at φ = π/2. For St = 0.5 this diﬀerence is 21.7%. Results indicate that adding an upstream prolate spheroid body does not significantly alter thrust results, though it does provide a small (nearly negligible) boost. Vorticity from the body is pulled downstream from the pitching foils, which interacts with the vortex generation when the vortex being generated is of the same sign as the body vorticity. This body vorticity does not aﬀect the vorticity magnitude of the downstream vortex pairs.

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18

Brzozowski, Daniel Paul. "Dynamic control of aerodynamic forces on a moving platform using active flow control." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42930.

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The unsteady interaction between trailing edge aerodynamic flow control and airfoil motion in pitch and plunge is investigated in wind tunnel experiments using a two degree-of-freedom traverse which enables application of time-dependent external torque and forces by servo motors. The global aerodynamic forces and moments are regulated by controlling vorticity generation and accumulation near the trailing edge of the airfoil using hybrid synthetic jet actuators. The dynamic coupling between the actuation and the time-dependent flow field is characterized using simultaneous force and particle image velocimetry (PIV) measurements that are taken phase-locked to the commanded actuation waveform. The effect of the unsteady motion on the model-embedded flow control is assessed in both trajectory tracking and disturbance rejection maneuvers. The time-varying aerodynamic lift and pitching moment are estimated from a PIV wake survey using a reduced order model based on classical unsteady aerodynamic theory. These measurements suggest that the entire flow over the airfoil readjusts within 2-3 convective time scales, which is about two orders of magnitude shorter than the characteristic time associated with the controlled maneuver of the wind tunnel model. This illustrates that flow-control actuation can be typically effected on time scales that are commensurate with the flow's convective time scale, and that the maneuver response is primarily limited by the inertia of the platform.

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19

Knapke, Clint J. "Aerodynamics of Fan Blade Blending." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1567517259599736.

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20

Boyd, David Douglas Jr. "Rotor/Fuselage Unsteady Interactional Aerodynamics: A New Computational Model." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/28591.

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A new unsteady rotor/fuselage interactional aerodynamics model has been developed. This model loosely couples a Generalized Dynamic Wake Theory (GDWT) to a Navier-Stokes solution procedure. This coupling is achieved using a newly developed unsteady pressure jump boundary condition in the Navier-Stokes model. The new unsteady pressure jump boundary condition models each rotor blade as a moving pressure jump which travels around the rotor azimuth =and is applied between two adjacent planes in a cylindrical, non-rotating grid. Comparisons are made between predictions using this new model and experiments for an isolated rotor and for a coupled rotor/fuselage configuration.
Ph. D.

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21

Parker, Colin M. "An Investigation into the Aerodynamics Surrounding Vertical-Axis Wind Turbines." Thesis, The George Washington University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10687173.

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The flow surrounding a scaled model vertical-axis wind turbine (VAWT) at realistic operating conditions was studied. The model closely matches geometric and dynamic properties—tip-speed ratio and Reynolds number—of a full-size turbine. The flowfield is measured using particle imaging velocimetry (PIV) in the mid-plane upstream, around, and after (up to 4 turbine diameters downstream) the turbine, as well as a vertical plane behind the turbine. Ensemble-averaged results revealed an asymmetric wake behind the turbine, regardless of tip-speed ratio, with a larger velocity deficit for a higher tip-speed ratio. For the higher tip-speed ratio, an area of averaged flow reversal is present with a maximum reverse flow of –0.04U_∞. Phase-averaged vorticity fields—achieved by syncing the PIV system with the rotation of the turbine—show distinct structures form from each turbine blade. There are distinct differences in the structures that are shed into the wake for tip-speed ratios of 0.9, 1.3 and 2.2—switching from two pairs to a single pair of shed vortices—and how they convect into the wake—the middle tip-speed ratio vortices convect downstream inside the wake, while the high tip-speed ratio pair is shed into the shear layer of the wake. The wake structure is found to be much more sensitive to changes in tip-speed ratio than to changes in Reynolds number. The geometry of a turbine can influence tip-speed ratio, but the precise relationship among VAWT geometric parameters and VAWT wake characteristics remains unknown. Next, we characterize the wakes of three VAWTs that are geometrically similar except for the ratio of the turbine diameter (D), to blade chord (c), which was chosen to be D/c = 3, 6, and 9, for a fixed freestream Reynolds number based on the blade chord of Re_c =16,000. In addition to two-component PIV and single-component constant temperature anemometer measurements are made at the horizontal mid-plane in the wake of each turbine. Hot-wire measurement locations are selected to coincide with the edge of the shear layer of each turbine wake, as deduced from the PIV data, which allows for an analysis of the frequency content of the wake due to vortex shedding by the turbine. Changing the tip-speed ratio leads to substantial wake variation possibly because changing the tip-speed ratio changes the dynamic solidity. In this work, we achieve a similar change in dynamic solidity by varying the D/c ratio and holding the tip-speed ratio constant. This change leads to very similar characteristic shifts in the wake, such as a greater blockage effect, including averaged flow reversal in the case of high dynamic solidity (D/c = 3). The phase-averaged vortex identification shows that both the blockage effect and the wake structures are similarly affected by a change in dynamic solidity. At lower dynamic solidity, pairs of vortices are shed into the wake directly downstream of the turbine. For all three models, a vortex chain is shed into the shear layer at the edge of the wake where the blade is processing into the freestream.

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22

Honohan, Andrew M. "The interaction of synthetic jets with cross flow and the modification of aerodynamic surfaces." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/20836.

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23

劉國強 and Kwok-keung Lau. "Interactions of coherent structures in annular jets." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1991. http://hub.hku.hk/bib/B31232632.

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24

With, Govert de. "Dynamic grid adaptation applied to large eddy simulation turbulence modelling." Thesis, University of Hertfordshire, 2001. http://hdl.handle.net/2299/14049.

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At present a large number of fluid dynamics applications are found in aerospace, civil and automotive engineering, as well as medical related fields. In many applications the flow field is turbulent and the computational modelling of such flows remains a difficult task. To resolve all turbulent flow phenomena for flow problems where turbulence is of key interest is a priori not feasible in a Computational Fluid Dynamics (CFD) investigation with a conventional mesh. The use of a Dynamic Grid Adaptation (DGA) algorithm in a turbulent unsteady flow field is an appealing technique which can reduce the computational costs of a CFD investigation. A refinement of the numerical domain with a DGA algorithm requires reliable criteria for mesh refinement which reflect the complex flow processes. At present not much work has been done to obtain reliable refinement criteria for turbulent unsteady flow. The purpose of the work presented in this thesis is to use both a DGA algorithm and Large Eddy Simulation (LES) turbulence model for predicting turbulent unsteady flow. The criteria for mesh refinement used in this work are derived from the equation for turbulent viscosity in the LES turbulence model. By using a modification to the turbulent viscosity as a refinement variable there is a link between both DGA algorithm and turbulence model. The smaller scale turbulence is modelled via the LES turbulence model, while the larger scales are resolved. In comparison with the simulations using a conventional mesh, substantial reduction in mesh size has been obtained with the use of a DGA algorithm. The reduction in mesh size is obtained without a decay in the quality of the prediction. It is shown that the use of a DGA algorithm in the context of turbulence modelling is a suitable tool which can be used as a next step in an attempt to resolve turbulence more realistically.

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25

Thomason, Nicole M. "Experimental Investigation of Suction Slot Geometry on a Goldschmied Propulsor." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/689.

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The Goldschmied Propulsor concept combines boundary layer suction and boundary layer ingestion to improve propulsive efficiency and reduce drag on an axisymmetric body. This investigation of a Goldschmied Propulsor aimed to determine influential characteristics of the suction slot geometry to aid in better slot geometry design and to decrease the suction flow requirements for maintaining attached flow over the entire model surface. The Propulsor model was 38.5 inches in length with a max diameter of 13.5 inches. Three suction slot geometries were investigated with the addition of aluminum cusps to the slot entrance. The cusps varied in the distance they protruded into the incoming suction flow and in the angle they took from the lip into the suction slot. Wind tunnel testing was completed in the Cal Poly 3ft x 4ft test section of the draw-down tunnel at a Reynolds Number of 2.3x106. Results show that of the three cusp geometries, the smallest Cusp A protruding only 0.05 inches into the suction flow, produced the greatest reductions in pressure drag and total axial force for the fan speeds tested. When compared to the no cusp condition, none of the three cusp geometries produced any significant improvement in total drag or in required suction flow rate.

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26

Erlhoff, Ethan Bruce. "Distributed Forcing on a 3D Bluff Body with a Blunt Base, An Experimental Active Drag Control Approach." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/879.

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This paper seeks to explore the effects of an active drag control method known as distributed forcing on a 3D bluff body with a blunt base. The 9.5 x 15.25 x 3 inch aluminum model constructed for this experiment has an elliptically shaped nose and rectangular aft section. The model is fitted with four, 12 Volt fans, forcing the freestream air into and out of 1 mm thick slots on the upper and lower trailing edges. The forcing is steady in time, held at a constant forcing velocity though all Reynolds numbers, but varies roughly sinusoidally in the spanwise direction across the model. Testing was conducted at Reynolds numbers of 50,000, 100,000 and 150,000 at California Polytechnic State University, San Luis Obispo in the Aerospace Engineering Department’s subsonic 3’ by 4’ wind tunnel. Effectiveness of the distributed forcing method was evaluated by measuring the base pressure on the model using a Scanivalve system. By measuring multiple static pressure ports, it was found that base pressure increased by 15.3% and 4.2% at Reynolds numbers of 50,000 and 100,000 respectively, and showed a decrease of 2.7% at a Reynolds number of 150,000. Total drag on the model was also measured using a sting balance mount fitted with strain gauges. This test showed a drag reduction of 15.8% and 5.5% for Reynolds numbers of 50,000 and 100,000 respectively, and an increase in drag of 2.0% at Reynolds number of 150,000, when omitting external power required to run the forcing assembly. The forcing assembly was shown to require nearly 12 times the power to operate than it saves in drag reduction at Reynolds number of 50,000. In addition, a thermal anemometry measurement of streamwise velocity of the near wake behind the bluff body was conducted to qualitatively assess the attenuation of the vortex street behind the model. Distributed forcing shows that as the freestream velocity is increased as compared to the forcing velocity, the change in energy spectral density is lessened, and as such, the largest attenuation in vortex shedding is at Reynolds number of 50,000 while nearly no change is seen at the Reynolds number of 150,000.

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27

Giles, David Michael. "Aerodynamic Performance Enhancement of a NACA 66-206 Airfoil Using Supersonic Channel Airfoil Design." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/186.

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Supersonic channel airfoil design techniques have been shown to significantly reduce drag in high-speed flows over diamond shaped airfoils by Ruffin and colleagues. The effect of applying these techniques to a NACA 66-206 airfoil is presented. The design domain entails channel heights of 8-16.6% thickness-to-chord and speeds from Mach 1.5-3.0. Numerical simulations show an increase in the lift-to-drag ratio for airfoils at Mach 2.5 at a 35,000-ft altitude with a 12% channel height geometry showing a benefit of 17.2% at 6-deg angle of attack and a sharp channel leading edge. Wave drag is significantly reduced while viscous forces are slightly increased because of greater wetted area. Lift forces compared to clean airfoil solutions were also decreased, due mainly to the reduction in the length of the lifting surfaces. A tensile yield failure structural analysis of a typical beam found an 11.4% channel height could be implemented over 50% of the span between two typical ribs. A three dimensional wing was designed with the determined slot geometry and two dimensional flow analyses. An overall increase in L/D of 9% was realized at Mach 2.5 at a 35,000-ft altitude and 6-deg angle of attack.

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28

Bhattacharya, Samik Ahmed Anwar. "Effect of three dimensional forcing on the wake of a circular cylinder." Auburn, Ala, 2009. http://hdl.handle.net/10415/1852.

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29

ROUSSEAU, Yannick, Igor MEN'SHOV, and Yoshiaki NAKAMURA. "Morphing-Based Shape Optimization in Computational Fluid Dynamics." 日本航空宇宙学会, 2007. http://hdl.handle.net/2237/13876.

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30

Diedrichs, Ben. "Studies of Two Aerodynamic Effects on High-Speed Trains : Crosswind Stability and Discomforting Car Body Vibrations Inside Tunnels." Doctoral thesis, Stockholm : School of engineering sciences, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4174.

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31

Davis, Jake Daniel. "A Higher-Order Method Implemented in an Unstructured Panel Code to Model Linearized Supersonic Flows." DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/1968.

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Since their conception in the 1960s, panel codes have remained a critical tool in the design and development of air vehicles. With continued advancement in computational technologies, today's codes are able to solve flow fields around arbitrary bodies more quickly and with higher fidelity than those that preceded them. Panel codes prove most useful during the conceptual design phase of an air vehicle, allowing engineers to iterate designs, and generate full solutions of the flow field around a vehicle in a matter of seconds to minutes instead of hours to days using traditional CFD methods. There have been relatively few panel codes with the capacity to solve supersonic flow fields, and there has been little recently published work done to improve upon them. This work implements supersonic potential flow methods into Cal Poly’s open source panel code, CPanel. CPanel was originally developed to solve steady, subsonic flows utilizing constant strength source and doublet panels to define the geometry, and an unstructured geometry discretization; it was later extended to include viscous vortex particle wakes and transient modeling. In this thesis, a higher-order method is implemented in CPanel for use in solving linearized supersonic flows, where a higher-order method is one that utilizes at least one singularity element whose order is higher than constant. CPanel results are verified against analytical solutions, such as the Taylor-Maccoll solution for supersonic conical flows and 2D shock-expansion theory, and the PANAIR and MARCAP supersonic panel codes. Results correlate well with the analytical solutions, and show strong agreement with the other codes.

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32

Powell, Jonathan D. "Impact of leading-edge orientation and shape on performance of a compressor blade." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Jun%5FPowell.pdf.

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33

Schmidt, Erin Stivers. "Electro-Drop Bouncing in Low-Gravity." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4441.

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We investigate the dynamics of spontaneous jumps of water drops from electrically charged superhydrophobic dielectric substrates during a sudden step reduction in gravity level. In the brief free-fall environment of a drop tower, with a non-homogeneous external electric field arising due to dielectric surface charges (with surface potentials 0.4-1.8 kV), body forces acting on the jumped drops are primarily supplied by polarization stress and Coulombic attraction instead of gravity. This electric body force leads to a drop bouncing behavior similar to well-known phenomena in 1-g0, though occurring for much larger drops (~0.5 mL). We show a simple model for the phenomenon, its scaling, and asymptotic estimates for drop time of flight in two regimes: at short-times close to the substrate when drop inertia balances Coulombic force due to net free charge and image charges in the dielectric substrate and at long-times far from the substrate when drop inertia balances free charge Coulombic force and drag. The drop trajectories are controlled primarily by the dimensionless electrostatic Euler number Eu, which is a ratio of inertial to electrostatic forces. To experimentally determine values of Eu we conduct a series of drop tower experiments where we observe the effects of drop volume, net free charge, and static surface potential of the superhydrophobic substrate on drop trajectories. We use a direct search optimization to obtain a Maximum Likelihood Estimate for drop net charge, as we do not measure it directly in experiment. For φEu/8π > 1 drops escape the electric field, where φ is a drop to substrate aspect ratio. However, we do not observe any escapes in our dataset. With an eye towards engineering applications we consider the results in light of the so-called low-gravity phase separation problem with a worked example.

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34

Bangalore, Ashok K. "Computational fluid dynamic studies of high lift rotor systems using distributed computing." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12949.

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35

Sohn, Myonghan. "A numerical study of the Weis-Fogh mechanism." Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/12000.

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36

Lieber, Baruch Barry. "Ordered and random structures in pulsatile flow through constricted tubes." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/13011.

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37

Vukasinovic, Jelena. "Flow in the gap between a rotating screw and a co-axial stationary outer cylinder." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17304.

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38

Reardon, Jonathan Paul. "Computational Analysis of Transient Unstart/Restart Characteristics in a Variable Geometry, High-Speed Inlet." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/95883.

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This work seeks to analyze the transient characteristics of a high-speed inlet with a variable-geometry, rotating cowl. The inlet analyzed is a mixed compression inlet with a compression ramp, sidewalls and a rotating cowl. The analysis is conducted at nominally Mach 4.0 wind tunnel conditions. Advanced Computational Fluid Dynamics techniques such as transient solutions to the Unsteady Reynolds-averaged Navier-Stokes equations and relative mesh motion are used to predict and investigate the unstart and restart processes of the inlet as well as the associated hysteresis. Good agreement in the quasi-steady limit with a traditional analysis approach was obtained. However, the new model allows for more detailed, time-accurate information regarding the fully transient features of the unstart, restart, and hysteresis to be obtained that could not be captured by the traditional, quasi-steady analysis. It is found that the development of separated flow regions at the shock impingement points as well as in the corner regions play a principal role in the unstart process of the inlet. Also, the hysteresis that exists when the inlet progresses from the unstarted to restarted condition is captured by the time-accurate computations. In this case, the hysteresis manifests itself as a requirement of a much smaller cowl angle to restart the inlet than was required to unstart it. This process is shown to be driven primarily by the viscous, separated flow that sets up ahead of the inlet when it is unstarted. In addition, the effect of cowl rotation rate is assessed and is generally found to be small; however, definite trends are observed. Finally, a rigorous assessment of the computational errors and uncertainties of the Variable-Cowl Model indicated that Computation Fluid Dynamics is a valid tool for analyzing the transient response of a high-speed inlet in the presence of unstart, restart and hysteresis phenomena. The current work thus extends the state of knowledge of inlet unstart and restart to include transient computations of contraction ratio unstart/restart in a variable-geometry inlet.
Doctor of Philosophy
Flight at high speeds requires efficient engine operation and performance. As the vehicle traverses through its flight profile, the engine will undergo changes in operating conditions. At high speeds, these changes can lead to significant performance loss and can be detrimental to the vehicle. It is, therefore, important to develop tools for predicting characteristics of the engine and its response to disturbances. Computational Fluid Dynamics is a common method of computing the fluid flow through the engine. However, traditionally, CFD has been applied to predict the static performance of an engine. This work seeks to advance the state of the art by applying CFD to predict the transient response of the engine to changes in operating conditions brought about by a variable geometry inlet with rotating components.

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39

Cordero, Samuel F. "Investigation of performance improvements including application of inlet guide vanes to a cross-flow fan." Thesis, Monterey, Calif. : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Sep/09Sep_Cordero.pdf.

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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, September 2009.
Thesis Advisor(s): Hobson, Garth V. ; Gannon, Anthony. "September 2009." Author(s) subject terms: Fan, cross-flow, crossflow, inlet guide vanes, thrust vectoring, vertical take off. Description based on title screen as viewed on Nov. 5, 2009. Includes bibliographical references (p. 95). Also available in print.

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40

Cohen, David E. II. "Trim Angle of Attack of Flexible Wings Using Non-Linear Aerodynamics." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30404.

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Multidisciplinary interactions are expected to play a significant role in the design of future high-performance aircraft (Blended-Wing Body, Truss-Braced wing, High Speed Civil transport, High-Altitude Long Endurance aircraft and future military aircraft). Also, the availability of supercomputers has made it now possible to employ high-fidelity models (Computational Fluid Dynamics for fluids and detailed finite element models for structures) at the preliminary design stage. A necessary step at that stage is to calculate the wing angle-of-attack at which the wing will generate the desired lift for the specific flight maneuver. Determination of this angle, a simple affair when the wing is rigid and the flow regime linear, becomes difficult when the wing is flexible and the flow regime non-linear. To solve this inherently nonlinear problem, a Newton's method type algorithm is developed to simultaneously calculate the deflection and the angle of attack. The present algorithm requires the sensitivity of the aerodynamic pressure with respect to each of the generalized displacement coordinates needed to represent the structural displacement. This sensitivity data is easy to determine analytically when the flow regime is linear. The present algorithm uses a finite difference method to obtain these sensitivities and thus requires only the pressure data and the surface geometry from the aerodynamic model. This makes it ideally suited for nonlinear aerodynamics for which it is difficult to obtain the sensitivity analytically. The present algorithm requires the CFD code to be run for each of the generalized coordinates. Therefore, to reduce the number of generalized coordinates considerably, we employ the modal superposition approach to represent the structural displacements. Results available for the Aeroelastic Research Wing (ARW) are used to evaluate the performance of the modal superposition approach. Calculations are made at a fixed angle of attack and the results are compared to both the experimental results obtained at NASA Langley Research Center, and computational results obtained by the researchers at NASA Ames Research Center. Two CFD codes are used to demonstrate the modular nature of this research. Similarly, two separate Finite Element codes are used to generate the structural data, demonstrating that the algorithm is not dependent on using specific codes. The developed algorithm is tested for a wing, used for in-house aeroelasticity research at Boeing (previously McDonnell Douglas) Long Beach. The trim angle of attack is calculated for a range of desired lift values. In addition to the Newton's method algorithm, a non derivative method (NDM) based on fixed point iteration, typical of fixed angle of attack calculations in aeroelasticity, is employed. The NDM, which has been extended to be able to calculate trim angle of attack, is used for one of the cases. The Newton's method calculation converges in fewer iterations, but requires more CPU time than the NDM method. The NDM, however, results in a slightly different value of the trim angle of attack. It should be noted that NDM will converge in a larger number of iterations as the dynamic pressure increases. For one value of the desired lift, both viscous and inviscid results were generated. The use of the inviscid flow model while not resulting in a markedly different value for the trim angle of attack, does result in a noticeable difference both in the wing deflection and the span loading when compared to the viscous results. A crude (coarse-grain) parallel methodology was used in some of the calculations in this research. Although the codes were not parallelized, the use of modal superposition made it possible to compute the sensitivity terms on different processors of an IBM SP/2. This resulted in a decrease in wall clock time for these calculations. However, even with the parallel methodology, the CPU times involved may be prohibitive (approximately 5 days per Newton iteration) to any practical application of this method for wing analysis and design. Future work must concentrate on reducing these CPU times. Two possibilities: (i) The use of alternative basis vectors to further reduce the number of basis vectors used to represent the structural displacement, and (ii) The use of more efficient methods for obtaining the flow field sensitivities. The former will reduce the number of CFD analyses required the latter the CPU time per CFD analysis. NOTE: (03/2007) An updated copy of this ETD was added after there were patron reports of problems with the file.
Ph. D.

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41

Mezynski, Alexis. "Measurements of pressure and thermal wakes in a transonic turbine cascade." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06112009-063252/.

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42

Fridlyand, Alex A. "Statistical properties of ideal two dimensional fluid flows : a numerical study." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12227.

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43

Janakiraman, S. V. "Fluid flow and heat transfer in transonic turbine cascades." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06112009-063614/.

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44

Bradshaw, Christopher John. "An experimental investigation of flapping wing aerodynamics in micro air vehicles." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FBradshaw.pdf.

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Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, June 2003.
Thesis advisor(s): Kevin D. Jones, Max F. Platzer. Includes bibliographical references (p. 89). Also available online.

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45

Beardsley, Colton Tack. "Computational Fluid Dynamics Analysis in Support of the NASA/Virginia Tech Benchmark Experiments." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99091.

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Computational fluid dynamics methods have seen an increasing role in aerodynamic analysis since their first implementation. However, there are several major limitations is these methods of analysis, especially in the area of modeling separated flow. There exists a large demand for high-fidelity experimental data for turbulence modeling validation. Virginia Tech has joined NASA in a cooperative project to design and perform an experiment in the Virginia Tech Stability Wind Tunnel with the purpose of providing a benchmark set of data for the turbulence modeling community for the flow over a three-dimensional bump. This process requires thorough risk mitigation and analysis of potential flow sensitivities. The current study investigates several aspects of the experimental design through the use of several computational fluid dynamics codes. An emphasis is given to boundary condition matching and uncertainty quantification, as well as sensitivities of the flow features to Reynolds number and inflow conditions. Solutions are computed for two different RANS turbulence models, using two different finite-volume CFD codes. Boundary layer inflow parameters are studied as well as pressure and skin friction distribution on the bump surface. The shape and extent of separation are compared for the various solutions. Pressure distributions are compared to available experimental data for two different Reynolds numbers.
Master of Science
Computational fluid dynamics (CFD) methods have seen an increasing role in engineering analysis since their first implementation. However, there are several major limitations is these methods of analysis, especially in the area of modeling of several common aerodynamic phenomena such as flow separation. This motivates the need for high fidelity experimental data to be used for validating computational models. This study is meant to support the design of an experiment being cooperatively developed by NASA and Virginia Tech to provide validation data for turbulence modeling. Computational tools can be used in the experimental design process to mitigate potential experimental risks, investigate flow sensitivities, and inform decisions about instrumentation. Here, we will use CFD solutions to identify risks associated with the current experimental design and investigate their sensitivity to incoming flow conditions and Reynolds number. Numerical error estimation and uncertainty quantification is performed. A method for matching experimental inflow conditions is proposed, validated, and implemented. CFD data is also compared to experimental data. Comparisons are also made between different models and solvers.

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46

Remington, Alexander. "A Study of Non-Fluid Damped Skin Friction Measurements for Transonic Flight Applications." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/9789.

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A device was developed to directly measure skin friction on an external test plate in transonic flight conditions. The tests would take place on the FTF-II flight test plate mounted underneath a NASA F-15 aircraft flying at altitudes ranging from 15,000 to 45,000 ft. at Mach numbers ranging from 0.70 to 0.99. These conditions lead to predicted shear levels ranging from 0.3 to 1.5 psf. The gage consisted of a floating element cantilevered beam configuration that was mounted into the surface of the test plate in a manner non-intrusive to the flow it was measuring. Strain gages mounted at the base of the beam measured the small strains that were generated from the shear forces of the flow. A non-nulling configuration was designed such that the deflection of the floating head due to the shear force from the flow was negligible. Due to the large vibration levels of up to 8 grms that the gage would experience during transonic flight, a vibration damping mechanism needed to be implemented. Viscous damping had been used in previous attempts to passively dampen the vibrations of skin friction gages in other applications, yet viscous damping proved to be an undesirable solution due to its leakage problems and maintenance issues. Three methods of damping the gage without a fluid filled damper were tested. Each gage was built of aluminum in order to maintain constant material properties with the test plate. The first prototype used a small internal gap and damping properties of air to reduce the vibration levels. This damping method proved to be too weak. The second prototype utilized eddy current damping from permanent magnets to dampen the motion of the gage. This mechanism provided better damping then the first prototype, yet greater damping was desired. The third method utilized eddy current damping from an electromagnet to dampen the motion of the gage. The eddy current damper achieved a much larger reduction in the vibration characteristics of the gage than the previous designs. In addition, the gage was capable of operating at various levels of damping. A maximum peak amplitude reduction of 33 % was calculated, which was less than theoretical predictions. The damping results from the electromagnetic gage provided an adequate level of damping for wind tunnel tests, yet increased levels of damping need to be pursued to improve the skin friction measurement capabilities of these gages in environments with extremely high levels of vibration. The damping provided by the electromagnet decreased the deflections of the head during 8 grms and 2 grms random noise vibrations bench tests. This allowed for a greater survivability of the gage. In addition, the reduction of the peak amplitude provided output with vibration induced noise levels ranging from 24 % to 5.9 % of the desired output of the gage. The gage was tested in a supersonic wind tunnel at shear levels of tw=3.9 to 5.3 psf. The shear levels encountered during wind tunnel verification tests were slightly larger than the shear levels encountered on the F-15 flight test plate during the flight tests, but the wind tunnel shear levels were considered adequate for verification purposes. The experimentally determined shear level results compared well with theoretical calculations
Master of Science

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47

Hariharan, Nathan. "High order simulation of unsteady compressible flows over interacting bodies with overset grids." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12960.

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48

Agsarlioglu, Ekin. "Numerical Investigations Of Lateral Jets For Missile Aerodynamics." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613585/index.pdf.

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In this thesis, effects of sonic lateral jets on aerodynamics of missiles and missilelike geometries are investigated numerically by commercial Computational Fluid Dynamics (CFD) software FLUENT. The study consists of two parts. In the first part, two generic missile-like geometries with lateral jets, of which experimental data are available in literature, are analyzed by the software for validation studies. As the result of this study, experimental data and CFD results are in good agreement with each other in spite of some discrepancies. Also a turbulence model study is conducted by one of test models. It is also found out that k-&epsilon
turbulence model is the most suitable model for this kind of problems in terms of accuracy and ease of convergence. In the second part of the thesis, parametric studies are conducted on a generic supersonic missile, NASA TCM, to see the effect of jet parameters on missile and component force and moments in pitch plane. Variable parameters are jet location, jet mass flow rate and angle of attack. As a result, it was found out that downstream influence zone of jet exit is more than the upstream influence zone. Normal force occurring by the interaction of the free stream and jet plume are amplified whenever the jet exit is located between lifting surfaces. Greater pitching moments are obtained when the jet exit moment arm with respect to moment reference center or jet mass flow rate is increased.

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49

Seubert, Cory A. "ANALYSIS OF A GOLDSCHMIED PROPULSOR USING COMPUTATIONAL FLUID DYNAMICS REFERENCING CALIFORNIA POLYTECHNIC’S GOLDSCHMIED PROPULSOR TESTING." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/844.

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The Goldschmied Propulsor is a concept that was introduced in mid 1950's by Fabio Goldschmied. The concept combines boundary layer suction and boundary layer ingestion technologies to reduce drag and increase propulsor efficiency. The most recent testing, done in 1982, left questions concerning the validity of the results. To answer these questions a 38.5in Goldschmied Propulsor was constructed and tested in Cal Poly's 3x4ft wind tunnel. The focus of their wind tunnel investigation was to replicate Goldschmied's original testing and increase the knowledge base on the subject. The goal of this research was to create a computational fluid dynamics (CFD) model to help visualize the flow phenomenon and see how well CFD was able to replicate Cal Poly’s wind tunnel results. CFD cases were run to get a comparison of the computational model and the wind tunnel results. For the straight tunnel geometry for the 0.385” slot and cusp A we found a body, pressure and friction drag, fan off CD of 0.0526 and a fan on at 500 Pascals with a CD of 0.0545. This is similar to the wind tunnel results but because of large errors in measuring overall drag we are not able to directly compare to the wind tunnel results. Overall we see that the trends match, mainly that the fan does not decrease the total pressure drag. This was a result of poor geometry and high fan speeds needed for attachment. The tested geometry is less than ideal and has a long way to go before it is of a shape that would have the potential to reduce the pressure drag as much as Goldschmied claimed. Future efforts should be put forth optimizing the aft body to reduce the low pressure in front of the slot and improving aft entrance of the slot to allow for a smoother flow.

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50

Tang, Wei. "Numerical solutions of unsteady flow past rotor sections." Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/13336.

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