Academic literature on the topic 'Minimized radiated power'
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Journal articles on the topic "Minimized radiated power"
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Hall, H. R., W. Brent Ferren, and R. J. Bernhard. "Active Control of Radiated Sound from Ducts." Journal of Vibration and Acoustics 114, no. 3 (July 1, 1992): 338–46. http://dx.doi.org/10.1115/1.2930267.
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The noise radiated by duct and pipe systems is modeled in the laboratory using a circular duct driven by a speaker at one end. Active control is achieved using a control speaker located adjacent to the open end of the duct. The objective of the investigation was to minimize the total sound power radiated by the duct and a single secondary source. However, the adaptive algorithm used by the controller for this investigation seeks to cancel the acoustic pressure only at a single location; that is, the location of the “error” microphone. Analytical studies predict that in order for the total sound power radiated by primary and secondary sources to be minimized, a single secondary source must radiate sound which is of approximately equal magnitude and opposite phase to the noise source and the error microphone must be placed somewhere in the plane of minimum pressure of an ideal acoustic dipole. These analytical results were verified in part, for the case of the secondary source facing the same direction as the primary source in the plane of the pipe outlet. Other cases were studied where the control speaker was located outside the plane of the duct outlet. The performance improved for these alternative orientations for a wide range of error microphone positions. Measured sound power with and without active control is shown for a range of frequencies and error microphone locations for three configurations of the duct and control source.
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Giordano, J. A., K. A. Cunefare, and G. H. Koopmann. "An Experiment on Optimization of Active Noise Control on a Three-Dimensional Extended Radiator." Journal of Vibration and Acoustics 115, no. 1 (January 1, 1993): 53–58. http://dx.doi.org/10.1115/1.2930314.
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In this experiment, a 10.6 dB reduction in the total radiated sound power for an extended radiator was achieved via active control through optimization of active sources. An acoustic boundary element program was used to determine the magnitude and phase of the active sources which minimized the total radiated sound power. This paper details the experimental verification of the numerically predicted active source strengths using a box-shaped acoustic radiator. The top and bottom of the radiator were thin steel plates which were driven in one of their structural modes by an electromagnetic shaker. The four corners of the top plate were removed to accommodate baffled loudspeakers, representing the active sources. To provide precise control of the experiment, the driving signals to the shakers and loudspeakers were generated and monitored by a control computer. The experimental results agreed closely with the analytical prediction, confirming that the optimum reduction had been achieved for the primary and active source configuration. The measured sound pressure reductions in the acoustic field of the radiator ranged from 8 dB to 19 dB for the 1,1 structural mode of the plates.
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St. Pierre, R. L., and G. H. Koopmann. "A Design Method for Minimizing the Sound Power Radiated from Plates by Adding Optimally Sized, Discrete Masses." Journal of Mechanical Design 117, B (June 1, 1995): 243–51. http://dx.doi.org/10.1115/1.2836463.
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In this paper, a novel method for minimizing the sound power radiated from a structure is presented. The method involves placing strategically sized masses at specific locations on the structure’s surface. The minimization procedure modifies the shapes of the resonant modes of the structure in the frequency range of interest such that they are forced to radiate sound inefficiently. Because of this, they are referred to as “weak radiator” mode shapes. The method uses an optimization procedure that directly minimizes the radiated sound power from the surface of a plate in an infinite baffle. The procedure can be carried out for a single frequency or over a range of frequencies. Analytical sensitivities of sound power with respect to the design variables are developed and used in the optimization algorithm. Results on various test cases show sound power reductions of 10 dB or more even when several resonances are included in the frequency band. An acoustic intensity probe is used to experimentally verify the results for one test case. The experiment confirms the sound power reductions predicted by the optimization program.
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St. Pierre, R. L., and G. H. Koopmann. "A Design Method for Minimizing the Sound Power Radiated from Plates by Adding Optimally Sized, Discrete Masses." Journal of Vibration and Acoustics 117, B (June 1, 1995): 243–51. http://dx.doi.org/10.1115/1.2838669.
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In this paper, a novel method for minimizing the sound power radiated from a structure is presented. The method involves placing strategically sized masses at specific locations on the structure’s surface. The minimization procedure modifies the shapes of the resonant modes of the structure in the frequency range of interest such that they are forced to radiate sound inefficiently. Because of this, they are referred to as “weak radiator” mode shapes. The method uses an optimization procedure that directly minimizes the radiated sound power from the surface of a plate in an infinite baffle. The procedure can be carried out for a single frequency or over a range of frequencies. Analytical sensitivities of sound power with respect to the design variables are developed and used in the optimization algorithm. Results on various test cases show sound power reductions of 10 dB or more even when several resonances are included in the frequency band. An acoustic intensity probe is used to experimentally verify the results for one test case. The experiment confirms the sound power reductions predicted by the optimization program.
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Inoue, Katsumi, Masashi Yamanaka, and Masahiko Kihara. "Optimum Stiffener Layout for the Reduction of Vibration and Noise of Gearbox Housing." Journal of Mechanical Design 124, no. 3 (August 6, 2002): 518–23. http://dx.doi.org/10.1115/1.1480817.
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Dynamic excitation from the gears generates vibration modes in the gearbox which causes radiation of unwanted structure-borne noise. To reduce the noise as well as the vibration, the stiffened plate construction is frequently used for the housing, where the rib stiffener layout is the key to this design. In this paper, the most effective position of stiffeners in order to reduce the vibration and noise radiation is searched and discussed. The analysis considers first a plate fixed at edges and excited at its center, and then a simplified rectangular gearbox excited at the shaft bearing locations. The housing of a simplified single-stage gearbox is modeled by triangular finite shell elements. It is excited by a set of harmonic forces which are applied at the bearing positions. The rib stiffener is modeled by beam elements, and its optimum layout is searched by a genetic algorithm. The vibration energy is adopted as the objective function to be minimized for the design for low vibration. On the other hand, the radiated sound power is the objective function for low noise. Although the noise is caused by the vibration, the optimum stiffener layout to realize low noise is not always identical to the layout that yields low vibration because of the difference in radiation efficiency. This is numerically clarified first from the viewpoint of the vibration mode of a plate. In the case of the design for the gearbox housing concerned, the vibration mode which causes the difference in radiation efficiency is not presented. Consequently, the optimum stiffener is placed along the line from the point of excitation to a fixed point, which reduces the vibration deflection of the faces with bearings as well as the in-plane displacement of the bearings.
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Ranjbar, Mostafa, and Steffen Marburg. "Vibroacoustic Optimization of Mechanical Structures: A Controlled Random Search Approach." Advanced Materials Research 622-623 (December 2012): 158–61. http://dx.doi.org/10.4028/www.scientific.net/amr.622-623.158.
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A combination of controlled random search method and geometry modification concept is used to minimize the root mean square level of structure borne sound for a model. The structure is a rectangular plate made of steel. A specific frequency range for this porpuse is considered. The results show that this approach could produce significant reduction in the value of radiated sound power level of the structure within a limited time.
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Constans, E. W., G. H. Koopmann, and A. D. Belegundu. "THE USE OF MODAL TAILORING TO MINIMIZE THE RADIATED SOUND POWER OF VIBRATING SHELLS: THEORY AND EXPERIMENT." Journal of Sound and Vibration 217, no. 2 (October 1998): 335–50. http://dx.doi.org/10.1006/jsvi.1998.1799.
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Kılkış, Birol, Malik Çağlar, and Mert Şengül. "Energy Benefits of Heat Pipe Technology for Achieving 100% Renewable Heating and Cooling for Fifth-Generation, Low-Temperature District Heating Systems." Energies 14, no. 17 (August 30, 2021): 5398. http://dx.doi.org/10.3390/en14175398.
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This paper addresses the challenges the policymakers face concerning the EU decarbonization and total electrification roadmaps towards the Paris Agreement set forth to solve the global warming problem within the framework of a 100% renewable heating and cooling target. A new holistic model was developed based on the Rational Exergy Management Model (REMM). This model optimally solves the energy and exergy conflicts between the benefits of using widely available, low-temperature, low-exergy waste and renewable energy sources, like solar energy, and the inability of existing heating equipment, which requires higher exergy to cope with such low temperatures. In recognition of the challenges of retrofitting existing buildings in the EU stock, most of which are more than fifty years old, this study has developed a multi-pronged solution set. The first prong is the development of heating and cooling equipment with heat pipes that may be customized for supply temperatures as low as 35 °C in heating and as high as 17 °C in cooling, by which equipment oversizing is kept minimal, compared to standard equipment like conventional radiators or fan coils. It is shown that circulating pump capacity requirements are also minimized, leading to an overall reduction of CO2 emissions responsibility in terms of both direct, avoidable, and embodied terms. In this respect, a new heat pipe radiator prototype is presented, performance analyses are given, and the results are compared with a standard radiator. Comparative results show that such a new heat pipe radiator may be less than half of the weight of the conventional radiator, which needs to be oversized three times more to operate at 35 °C below the rated capacity. The application of heat pipes in renewable energy systems with the highest energy efficiency and exergy rationality establishes the second prong of the paper. A next-generation solar photo-voltaic-thermal (PVT) panel design is aimed to maximize the solar exergy utilization and minimize the exergy destruction taking place between the heating equipment. This solar panel design has an optimum power to heat ratio at low temperatures, perfectly fitting the heat pipe radiator demand. This design eliminates the onboard circulation pump, includes a phase-changing material (PCM) layer and thermoelectric generator (TEG) units for additional power generation, all sandwiched in a single panel. As a third prong, the paper introduces an optimum district sizing algorithm for minimum CO2 emissions responsibility for low-temperature heating systems by minimizing the exergy destructions. A solar prosumer house example is given addressing the three prongs with a heat pipe radiator system, next-generation solar PVT panels on the roof, and heat piped on-site thermal energy storage (TES). Results showed that total CO2 emissions responsibility is reduced by 96.8%. The results are discussed, aiming at recommendations, especially directed to policymakers, to satisfy the Paris Agreement.
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Alshabatat, Nabeel T., and Koorosh Naghshineh. "Optimization of Natural Frequencies and Sound Power of Beams Using Functionally Graded Material." Advances in Acoustics and Vibration 2014 (February 20, 2014): 1–10. http://dx.doi.org/10.1155/2014/752361.
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This paper presents a design method to optimize the material distribution of functionally graded beams with respect to some vibration and acoustic properties. The change of the material distribution through the beam length alters the stiffness and the mass of the beam. This can be used to alter a specific beam natural frequency. It can also be used to reduce the sound power radiated from the vibrating beam. Two novel volume fraction laws are used to describe the material volume distributions through the length of the FGM beam. The proposed method couples the finite element method (for the modal and harmonic analysis), Lumped Parameter Model (for calculating the power of sound radiation), and an optimization technique based on Genetic Algorithm. As a demonstration of this technique, the optimization procedure is applied to maximize the fundamental frequency of FGM cantilever and clamped beams and to minimize the sound radiation from vibrating clamped FGM beam at a specific frequency.
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Rambousky, R., J. Nitsch, and H. Garbe. "Matching the termination of radiating non-uniform transmission-lines." Advances in Radio Science 11 (July 4, 2013): 259–64. http://dx.doi.org/10.5194/ars-11-259-2013.
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Abstract. In this contribution a concept of matching the termination of radiating non-uniform transmission-lines is proposed. Using Transmission-Line Super Theory, position and frequency dependent line parameters can be obtained. Therefore, a characteristic impedance can be determined which is also position and frequency dependent. For a single wire transmission-line it could be shown that the maximum value of that characteristic impedance is an optimal termination in the sense of minimizing the variation of the current on the line. This indicates that matching is not a local effect at the position of the concentrated load but a cooperative process including the whole non-uniform transmission-line. In addition this choice of termination minimizes the variation of the radiated power over frequency.
Dissertations / Theses on the topic "Minimized radiated power"
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Anderson, Monty J. "Active Control of the Human Voice from a Sphere." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5295.
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This work investigates the application of active noise control (ANC) to speech. ANC has had success reducing tonal noise. In this work, that success was extended to noise that is not completely tonal but has some tonal elements such as speech. Limitations such as causality were established on the active control of human speech. An optimal configuration for control actuators was developed for a sphere using a genetic algorithm. The optimal error sensor location was found from exploring the nulls associated with the magnitude of the radiated pressure with reference to the primary pressure field. Both numerically predicted and experimentally validated results for the attenuation of single frequency tones were shown. The differences between the numerically predicted results for attenuation with a sphere present in the pressure field and monopoles in the free-field are also discussed.The attenuation from ANC of both monotone and natural speech is shown and a discussion about the effect of causality on the results is given. The sentence “Joe took father’s shoe bench out” was used for both monotone and natural speech. Over this entire monotone speech sentence, the average attenuation was 8.6 dB with a peak attenuation of 10.6 dB for the syllable “Joe”. Natural speech attenuation was 1.1 dB for the sentence average with a peak attenuation on the syllable “bench” of 2.4 dB. In addition to the lower attenuation values for natural speech, the pressure level for the word “took” was increased by 2.3 dB. Also, the harmonic at 420 Hz in the word “father’s” of monotone speech was reduced globally up to 20 dB. Based on the results of the attenuation of monotone and natural speech, it was concluded that a reasonable amount of attenuation could be achieved on natural speech if its correlation could approach that of monotone speech.
Conference papers on the topic "Minimized radiated power"
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Deng, Xiaolong, Zongjie Zhang, Chunpeng Sun, and Shaohe Li. "Genetic Algorithms for the Vibroacoustic Optimization of the Thin Parts of I.C. Engine." In ASME 2003 Internal Combustion Engine and Rail Transportation Divisions Fall Technical Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/icef2003-0750.
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The Noise Vibration Harshness (NVH) behavior of engines is one of the predominant factors for market acceptance of vehicles. To reach this goal it is necessary to reduce the absolute noise level and also the noise level in specific frequency ranges. The design of radiating structures for minimal sound radiation is a multidisciplinary problem that involves complex objective functions and expensive computations. In this paper, genetic algorithm is used as a promising tool for numerical optimization of such problems. The objective of the study is to determine effective, general design methods for determining the optimal design of thin parts of I.C. engine that minimizes the total radiated acoustic power. Variable attached discrete masses are considered. Acoustic response is minimized either at a single frequency or first five natural frequencies. Radiated sound power is calculated using a boundary element method, in conjunction with a finite element solver ANSYS for the solution of the structural acoustical problem.
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Wodtke, Hans-Walter, and Gary H. Koopmann. "Quieting Plate Modes With Optimally Sized Point Masses: A Volume Velocity Approach." In ASME 1995 Design Engineering Technical Conferences collocated with the ASME 1995 15th International Computers in Engineering Conference and the ASME 1995 9th Annual Engineering Database Symposium. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/detc1995-0456.
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Abstract The radiated sound power of the second symmetric mode of a clamped square plate is minimized by attaching optimally sized point masses to the plate. The plate is driven by a point force at its center and the positions of the masses are prescribed. The structural vibration problem is solved using a simple Rayleigh-Ritz approach. Solving the acoustic radiation problem is simplified by making a low-ka-assumption, i.e., the point masses are determined so as to minimize the surface volume velocity of the plate. The predicted results are verified experimentally by means of sound intensity measurements. It is shown that a structural resonance can be deleted from the acoustic response by exploiting volume velocity cancellation. The effects involved are illustrated in detail.
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Inoue, Katsumi, Masashi Yamanaka, and Masahiko Kihara. "Optimum Stiffener Layout for the Reduction of Vibration and Noise of Gearbox Housing." In ASME 2000 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/detc2000/ptg-14445.
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Abstract The vibration of gearbox housing causes the structure-borne noise. To reduce the noise as well as vibration, the stiffened plate construction is frequently used for the housing, and the rib stiffener layout is the key to this design. In this paper, the most effective position of stiffeners in reducing the vibration and noise radiation is searched and discussed. The housing of a simplified single stage gearbox is modeled by triangular finite shell elements. It is excited by a set of harmonic forces which are applied at the bearing positions. The rib stiffener is modeled by beam elements, and its optimum layout is searched by a genetic algorithm. The vibration energy is adopted as the objective function to be minimized in case of the design for low vibration. On the other hand, the radiated sound power is the objective function for low noise. Though the noise is caused by the vibration, the optimum layout of stiffener for low noise is not always identical with the layout for low vibration because of the difference of radiation efficiency. This is numerically-clarified first from the view point of vibration mode of a plate. In case of the design of the gearbox housing concerned, the vibration mode which causes the difference of radiation efficiency is neglected. Consequently, the optimum stiffener is placed along the line from the point of excitation to the fixed point, which reduces the vibration displacement of the faces with bearings.
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Moongilan, Dheena. "Method for direct interconnection of PCB power layer to chassis to minimize radiated emissions." In 2011 IEEE International Symposium on Electromagnetic Compatibility - EMC 2011. IEEE, 2011. http://dx.doi.org/10.1109/isemc.2011.6038305.
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Alshabatat, Nabeel T., and Koorosh Naghshineh. "A Design Approach for Improving the Vibroacoustic Characteristics of Plate Structures." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-62392.
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This paper presents a design method to optimize the natural frequencies and to minimize the radiated sound power from vibrating plate-like structures. The design method involves creating dimples on the surface of the structure. The dimple can be defined as a local modification in the surface of a structure which has a spherical shape. Creating dimples does not change structural mass but affects its stiffness. Also, addition of dimples alters the plate mode shapes and as a result changes the radiated sound power from the plate. This method is cost-effective in comparison with other structural dynamics modification methods because it can be achieved through a one-step manufacturing method and because it enhances the dynamic behavior of platelike structures without additional weight or added joints.
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Naik, Ravin G., Arvind S. Mohite, and Juneyd F. Dadi. "Experimental Evaluation of Heat Transfer Rate in Automobile Cooling System by Using Nanofluids." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-50571.
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The demand for more powerful engines in smaller hood spaces has created a problem of insufficient rates of heat dissipation in automotive radiators. Insufficient heat dissipation can result in the overheating of the engine, which leads to the breakdown of lubricating oil, metal weakening of engine parts, and significant wear between engine parts. To minimize the stress on the engine as a result of heat generation, automotive radiators must be redesigned to be more compact while still maintaining high levels of heat transfer performance. Moreover, this can be done without significant modification to the existing internal radiator structure, this can be done by increasing (i) heat transfer area, (ii) temperature, and (iii) heat transfer co-efficient. However, technologies have already reached their limit for the cases heat transfer area and temperature. Recently many researchers found that dispersing nano-sized particles into the liquids result in higher heat transfer co-efficient of these newly developed fluids called nanofluids compared to the traditional liquids. This kind of fluids are now of great interest not only for modifying heat transfer performance of fluids, but also for improving other different characteristics such as mass transfer and rheological properties of fluids. A major goal of the nanofluids project is to reduce the size and weight of the vehicle cooling systems by greater than 10% despite the cooling demands of higher power engines. Nanofluids enable the potential to allow higher temperature coolants and higher heat rejection in the automotive engines. It is estimated that a higher temperature radiator could reduce the radiator size approximately 30%. In this paper we have considered two nanofluids comprising of aluminium oxide and copper oxide in water mixture has been studied experimentally to compare their performance in automobile radiator. The study shows that for a particle volume concentration of 0.1%, both nano fluids show improvements in their performance over the base fluid. Comparison has been made on the basis of three important parameters; equal mass flow rate, equal air flow rate and equal radiator inlet temperature of coolant. For both nanofluids exhibit increase in heat transfer rate compared to base fluid.
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Tort Oropeza, Alejandro, Rogelio Gonza´lez Oropeza, and Fe´lix Nu´n˜ez Orozco. "A Different Combustion Engine." In ASME 2005 Internal Combustion Engine Division Spring Technical Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/ices2005-1007.
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This paper investigates the possibilities of an EXTERNAL COMBUSTION ENGINE (ECE) capable of attaining high thermodynamic efficiency and low emission of noxious gases. This ECE consists principally of an air compressor, a combustion chamber or combustor and an expansion or power cylinder. The compressed air is introduced into the combustor; the fuel is injected into the combustor, and a spark plug initiates the combustion. By performing the combustion in a combustor specially designed for that purpose, the combustion can be controlled and the generation of noxious gases can be reduced. The water that cools the jackets of the system is also injected into the combustor; by doing so, the temperature of the combustion products can be maintained at a value sufficiently low so as to minimize the formation of NOx, and at the same time, a significant part of the heat transmitted to the cooling water can be recuperated instead of being dissipated in a radiator. The water, already hot or evaporated, mixes with the combustion gases and expands in the power cylinder, participating in the generation of mechanical power. The efficiency of the cycle is increased.
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Forristall, George Z., and Alexia Aubault. "Diffraction Corrections for Platform Wave Measurements." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-24649.
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Many measurements of hurricane waves have been made from deep water production facilities in the Gulf of Mexico. Measurements made on different sides of the platforms differ from one another and the incident wave field because the platforms diffract and radiate waves. For many purposes, we would like to know the incident wave field. Forristall and Aubault (OMAE2013-10860) used WAMIT diffraction calculations to successfully invert wave spectra measured under a TLP model in the Marin offshore basin. We have now used similar techniques to invert spectra measured at offshore platforms during Hurricanes Gustav and Ike. We do not have any measurements of the undisturbed wave spectra for testing the results. The tests were made by checking whether inverse calculations on all the gauges deployed at different locations on the platforms could produce the same undisturbed wave field. Wave directions are needed for the diffraction calculations. Information from the wave gauges can be used to find the directions by optimizing the agreement among the inverted power spectra. To perform the optimization, we varied both the mean direction and spreading at each spectral frequency. The rms difference between the inverted probe spectral densities was minimized at each spectral frequency. When spectra from four gauges on a platform are inverted, they agree reasonably well with each other. The average of the inverted significant wave heights is slightly lower than the average of the measured significant wave heights. But when spectra from pairs of the four probes are inverted, the results differ depending on which pair is used. This result implies that our inversion method cannot be used on data from platforms with two probes, and casts doubt on the accuracy of four probe inversions.
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Savander, Brant R., Malcolm E. Willis, Karl A. Stambaugh, and Kelley A. Cox. "USCG Patrol Craft Hydrodynamic Fuel Efficiency Improvements." In SNAME 13th International Conference on Fast Sea Transportation. SNAME, 2015. http://dx.doi.org/10.5957/fast-2015-035.
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A computational analysis program, conducted at full scale, has been completed on the USCG Fast Response Cutter (FRC) to evaluate how appendage and propeller redesign affects calm water powering performance and erosive cavitation onset. Aft working forward, the geometric variations considered included: addition of a stern flap, wake adapted rudder redesign, propeller design refinement, wake adapted skeg redesign, and redesign of the spray rail system. The first activity was to use a wake alignment procedure to redesign the current rudder in an effort to improve the rudder drag characteristics and minimize or eliminate rudder cavitation. The wake aligned redesign eliminated rudder cavitation over the entire speed range, and decreased total drag by 6% at flank speed. Replacement of only the current rudders with the wake aligned redesign is predicted to increase flank speed from 28.9 knots to 29.4 knots. The stern flap and spray rail efforts followed the historical guidance of similar work performed on the USCG Island Class patrol boats, as documented in Cusanelli and Barry (2002). Following the geometric guidance of the Island Class stern flaps the final recommended stern flap for the FRC results in a brake power demand reduction of 15%. The Island Class achieved a 12% reduction in required brake power at similar speeds. The combination of the new stern flap, wake adapted rudders, current propeller, current skegs, and new spray rail yielded an increase in flank speed from 28.9 to 31.4 knots. Skeg redesign resulted in a 30% decrease in the magnitude of the radiated pressure pulse amplitudes experienced in the propeller tunnel above the propeller. The redesign of the skeg did not affect the propeller behind efficiency. Modification of the current propeller geometry was the final redesign task. The final system, which included the new stern flap, wake aligned rudders, redesigned propeller, wake aligned skegs, and new spray rail system decreased power by 18.6% at the prior 28.9 knot flank speed of FRC. The new flank speed, with the final system, has increased to 32.9 knots in the full load, end of service life condition. The combined effect of all redesign activities reveals an annual fuel consumption savings of 24,000 gallons per vessel per year, which corresponds to a 13.6% savings when compared to the original as-built system. Assuming a fuel cost of $4 per gallon, the annual cost savings per vessel per year equals $96,000. This savings extrapolated over a 58 ship fleet equates to $5.5 million in savings per year for the class. This saving per year yields a savings of $110 million for the 20-year operating life of the 58-ship class.
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Vunnam, Kiran, and Bruce Bouldin. "APU Exhaust Muffler Design Improvements Through Conjugate Heat Transfer CFD Analysis." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68850.
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An Auxiliary Power Unit (APU) is an additional gas turbine engine located in the tail cone section of an aircraft which can be operated while the aircraft is on the ground or in flight. It is used to generate electricity for the aircraft’s electrical systems and to provide air to the environmental control units (ECU’s) when the main engines are not operating or there is a desire to unload the main engines, such as in an engine out situation. The APU is also used for main engine starting. An APU typically has an exhaust system that vents out of the rear of the tail cone. When the APU is in operation, the exhaust emits a very loud noise which, if not muffled, could be an irritant to the members of the ground crew. To reduce the impact of this exhaust noise, the APU is commonly fitted with a muffler. The muffler is placed around the APU’s exhaust pipe so that all of the APU’s exhaust is channeled through the muffler. The muffler is designed and constructed to substantially reduce the intensity of the noise emitted by the APU exhaust. The muffler is made of metal and has a tendency to get very hot during operation of the APU because of the high temperature of the exhaust gasses generated by the APU. It has been observed that the temperatures on the outer skin of the muffler commonly reach above 1,000 degrees Fahrenheit. If the muffler is not insulated, this heat will radiate outward from the muffler to the tail cone. Modern aircraft tail cones are commonly made from composite materials to help keep the overall weight of the aircraft low. Such materials cannot tolerate the high temperatures radiating from the muffler and if exposed to such temperatures for any length of time, may experience some form of failure. Accordingly, aircraft manufactures commonly mandate that the heat radiating from the muffler not exceed a predetermined limit. So it is essential to design a muffler which not only attenuates the noise levels of the APU exhaust, but also need to be insulated with a low conductive insulated blanket around it. A conjugate heat transfer CFD analysis was performed on a new APU exhaust system to optimize the exhaust muffler blanket design. Several different blanket material types and configurations were analyzed to minimize the heat transfer through the muffler. The CFD analysis included many geometric details including the exhaust eductor, to better model the exhaust gas profile, the muffler baffles and the tail cone structure. Muffler blanket outer surface temperature values and tail cone skin temperatures were monitored to determine the optimum design. This paper discusses the CFD model and analysis and discusses the results. It explains the different design iterations needed to arrive at acceptable muffler blanket outer surface temperatures and tail cone skin temperatures.