Volume 1: Fluid Mechanics最新文献

{"title":"Discrete Vortex Modeling of a Flapping Foil With Activated Leading Edge Motion","authors":"M. Prier, J. Liburdy","doi":"10.1115/ajkfluids2019-4964","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4964","url":null,"abstract":"\u0000 Energy harvesting performance for a flapping foil device is evaluated to determine how activated leading edge motion affects the aerodynamic forces and the cycle power generated. Results are obtained for a thin flat foil that pitches about the mid-chord and operates in the reduced frequency range of k = fc/U of 0.06–0.10 and Reynolds numbers of 20,000 and 30,000 with a pitching amplitude of 70° and heaving amplitude of h0 = 0.5c. Time resolved data are presented based on direct force measurements and are used to determine overall cycle efficiency and coefficient of power. These results are compared against a panel-based discrete vortex model to predict power production. The model incorporates a leading edge suction parameter predictor for vortex shedding and empirical adjustments to circulatory forces. It is found that the leading edge motions that reduce the effective angle of attack early in a flapping stroke generate larger forces later in the stroke. Consequently, the energy harvesting efficiencies and power coefficients are increased since the generated aerodynamic loads are better synchronized with the foil motion. The efficiency gains are reduced with increasing reduced frequencies.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114425850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The CFD Modeling of the Water Braking Phenomena for the Holloman High-Speed Test Track","authors":"Jose Terrazas, V. Kotteda, Vinod Kumar, R. Edmonds, Michelle Zeisset","doi":"10.1115/ajkfluids2019-5506","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5506","url":null,"abstract":"\u0000 At the Holloman High-Speed Test Track (HHSTT), momentum exchange with water is used to decelerate sleds from very high speeds (> Mach 1). This process, at the HHSTT, is called ‘water braking’. Improving the prediction capabilities of water braking phenomena has the potential to result in radical changes in the designs of sleds, improve rocket sled velocity-time test profile predictions, provide greater confidence of braking mechanisms, and decrease risk in the recovery of critical infrastructures. Understanding the water?s behavior with the sled is critical to predicting how the water could damage the sled, which affects the recoverability of the sled and can determine the success of a mission. Traditionally, sled design for the test missions for water braking has been guided by empirical/hand calculations to estimate the forces on various components. The calculations involved various approximations in arriving at the force balance law and predicting the acceleration/deceleration profile. In partnership with the HHSTT, we performed preliminary simulations to develop a predictive model for the HHSTT sled tests at various velocity regimes. The (preliminary) CFD results from different geometry configurations for the sled and modeling parameters will be presented.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134061472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simulation of the Wake of the Flow Around Two Side-By-Side Circular Cylinders at Reynolds Number 5000","authors":"A. Jensen, H. Sørensen, J. Hærvig","doi":"10.1115/AJKFLUIDS2019-5442","DOIUrl":"https://doi.org/10.1115/AJKFLUIDS2019-5442","url":null,"abstract":"\u0000 Interaction between the wakes of two cylinders in side-by-side configuration creates interesting flow phenomena. The nature of the wake depends on the Reynolds number and the transverse pitch distance between the cylinders. The flow over two side-by-side cylinders of equal diameter is simulated in 3D at Reynolds number 5000 using Large Eddy Simulation (LES). The centre-to-centre transverse pitch ratio is varied and the flow behind the cylinders is classified into either a bi-stable flow regime with biased gap flow or a regime with parallel vortex streets. Furthermore, representative instantaneous flow fields, Strouhal number and the time varying drag coefficient C′D are presented.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132472484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Laser Velocity and Surface Measurements Toward the Prediction of Turbulent Frictional Resistance on Irregular Rough Surface in Higher Reynolds Number Range","authors":"K. Okubo, Shunpei Suzuki, Y. Kuwata, Y. Kawaguchi","doi":"10.1115/ajkfluids2019-5325","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5325","url":null,"abstract":"\u0000 In this research, we consider the relationship between roughness of the wall and frictional resistance in the range of high-Reynolds number regime which is important for practical use, and its goal is to build a more accurate and highly versatile formula for predicting the frictional resistance acting on the complex surface with irregular roughness. In addition to the parameter corresponding to the distribution of the roughness used in a conventional and empirical formula, we aim to construct an empirical formula including the parameter representing the wavelength of the rough surface. In this study, we conduct laboratory experiments of Taylor-Couette flow, using the cylindrical test specimens roughly sprayed with an actual ship paint, and investigate the influence of irregular roughness on flow field and the surface frictional stress based PIV (Particle Image Velocimetry) measurements and torque measurements in high Reynolds numbers. The azimuthal mean velocity for rough surfaces increased in the entire flow field in comparing to the flow for a smooth surface, and this tendency is remarkable in a bulk region. Also, we measure the rough surfaces of the specimens using a laser type one-shot three-dimensional measurement device. Based on the results of above measurements, we propose the direct relationship between the parameter of a rough surface and frictional resistance.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121614072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simulation-Based Approach to Science, Technology, Engineering, and Math Challenges","authors":"I. Milanović, T. Eppes, Kamau C. Wright","doi":"10.1115/ajkfluids2019-4864","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4864","url":null,"abstract":"\u0000 This paper discusses an undergraduate mechanical engineering (ME) curricular sequence of four required and four elective courses (4+4) in the area of modeling, simulation, and application development with the focus on the thermo-fluids topics. The purpose is early and consistent integration of knowledge and modern computational skills across curriculum. This approach facilitates a deeper understanding of complex theoretical concepts and engineering solutions by embedding modeling and simulations in required courses from the freshmen to the junior year. Professional electives provide an additional opportunity to apply the same strategy either in the concentration format or in one-off courses that individual students may decide to take.\u0000 The sequence starts with four courses that are required for all ME majors: Graphic Communication, Computer-Aided Design and Analysis, Fluid Mechanics, and Heat Transfer. Four additional courses are technical electives and a part of an undergraduate Computational Mechanical Engineering (Comp ME) concentration: Applied CFD, Multidisciplinary Modeling, Finite Element Analysis, and Convective Heat and Momentum Transfer. The first two required courses, Graphic Communication and Computer-Aided Design and Analysis, provide the foundation in model development. There can also be opportunities to embed simulations as a part select sophomore level courses, such as Thermo-dynamics. In the third year thermo-fluids sequence, as well as in the Comp ME technical electives, students gain experience creating models of new and existing systems, visualizing simulation results, going through the process of verification and validation, optimizing solutions, and building applications.\u0000 We will first present the rationale for adopting a simulation-based approach to Science, Technology, Engineering, and Math (STEM) challenges. Second, we will show how this high-impact approach can be implemented without additional labor-intensive work on the part of faculty members. Finally, special attention will be devoted to the required and elective thermo-fluids courses that use COMSOL Multiphysics® as the software platform. In each course, a series of models are created and documented in technical reports. Applications are also built based on the underlying models to complete the experience. The paper provides a detailed description of the technical content in each course, learning strategies, expected outcomes, and assessment criteria. Several examples illustrating student work are presented. How and why the courses evolved and were improved over time is included. Lastly, the importance and value of this approach in view of changes coming to the ABET criteria is discussed.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"11936 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123475110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Concentration Distribution of Photosensitive Liquid in a Droplet Under UV Light","authors":"Tianyi Li, A. Kar, Ranganathan Kumar","doi":"10.1115/ajkfluids2019-5519","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5519","url":null,"abstract":"\u0000 A semi-analytical solution for the concentration of photosensitive suspension is developed in a hemispherical droplet illuminated with UV laser. A biharmonic equation in stream function is analytically solved using toroidal coordinates and the velocity is then used to solve the mass transport equation for concentration. Flow pattern and photosensitive material concentration are affected by the peak location of the UV light intensity, which corresponds to a surface tension profile. When the laser beam is moved from the droplet center to its edge, a rotationally symmetric flow pattern changes from a single counter clockwise circulation to a circulation pair and finally to a single clockwise circulation. This modulation in the orientation of circulation modifies the concentration distribution of the photosensitive material. The distribution depends on both diffusion from the droplet surface as well as Marangoni convection. The region beneath the droplet surface away from the UV light intensity peak has low concentration, while the region near the downward dividing streamline has the highest concentration. When the UV light peak reaches the droplet edge, the concentration is high everywhere in the droplet.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125538103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Visualization of Three-Dimensional Flow Structures Caused by Rotating Instability","authors":"J. Peter, P. Thamsen","doi":"10.1115/ajkfluids2019-4930","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4930","url":null,"abstract":"\u0000 The present study deals with the flow phenomenon Rotating Instability (RI), which is predominantly observed in axial compressors at off-design conditions e.g. near stall. It potentially induces noise and triggers blade vibrations. Despite numerous studies, the characteristics and the source of RI are not completely understood. The objective of this work is to identify and to visualize characteristic flow topology corresponding to RI by means of Stereo High Speed Particle Image Velocimetry (PIV). The experimental investigations were carried out in an annular compressor stator cascade with and without hub clearance at an inflow Mach number of Ma = 0.4 and the Reynolds number of Re = 300 000. The time-resolved 3C flow field is measured in a single blade passage in planes tangential to the hub. Additionally, the time-resolved pressure fluctuations are captured synchronously to the PIV system. By using combined correlation techniques the spectral characteristics, the spatial extension of the RI and the characteristic flow structures were identified and visualized in configurations with and without hub clearance. The investigations point out that the general flow mechanism of RI is similar in compressor cascades with and without hub clearance. Overall, this work gives important insights into the complex phenomenon Rotating Instability, which can be taken into account when developing compressors in the future.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"199 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124464465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Effect of the Velocity Ratio on the Diffusion Inhibition of Coaxial Jet","authors":"Fujio Akagi, Takumi Etou, Y. Fukuda, Ryoya Yoshioka, Youichi Ando, Sumio Yamaguchi","doi":"10.1115/ajkfluids2019-5369","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5369","url":null,"abstract":"\u0000 The mixing characteristics of a coaxial round jet having inner to outer diameter ratio di/do = 0.67 was investigated to establish the method for mass and energy transport with inhibiting its diffusion. In the present study, the effect of the velocity ratio on the streamwise length of the potential core of the central round jet, the streamwise velocity distribution, and the evolution of vortcies of a coaxial jet was evaluated by using Large Eddy Simulation and experimental flow visualization to clarify diffusion inhibition mechanism of a central jet. Three velocity ratios γ = 0.25, 0.5, and 0.75 were conducted under a single condition of the central jet Reynolds number of 2000. The results show that the potential core length of a central jet become the longest on condition of the velocity ratio of 0.5, and the length was 15 times of the inner nozzle diameter. This value is equivalent to 3.8 times in the case of a general round jet. In other velocity ratio, it was also confirmed that the potential core length of a central jet becomes short by enhancement of vortices generation in the shear layer of annular and central jet. It is concluded that the velocity gradient in the shear layer is the important parameter in determining the diffusion of a central jet.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127497547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Parametric Study for Optimization of Blowing and Suction Locations for Improving Lift-to-Drag Ratio on a Clark-Y Airfoil","authors":"M. Ohashi, Y. Morita, Shiho Hirokawa, K. Fukagata, N. Tokugawa","doi":"10.1115/ajkfluids2019-5067","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5067","url":null,"abstract":"\u0000 In this study, Reynolds-averaged Navier-Stokes simulation (RANS) of the uniform blowing and suction (UB/US) control on a Clark-Y airfoil was performed aiming at improving an airfoil performance by friction drag reduction. First, the control effect when only the uniform blowing control or uniform suction control is applied on the airfoil surface was investigated by changing the control locations. The blowing or suction velocity was 0.14% of the free-stream velocity and the blowing/suction area was set at four different locations from the leading edge to the trailing edge on both the upper and lower surfaces. The Reynolds number based on the chord length is 1.5 × 106. The angle of attack is set to 0°. It was found that friction drag is decreased/increased by single UB/US control. It was also found that the lift-to-drag ratio improved with UB on the lower surface or US on the upper surface, and decreased with UB on the upper surface or US on the lower surface. In the combined control of UB and US, the blowing and suction velocity was 0.14% or 0.26% of the free-stream velocity and the locations of blowing/suction and flow conditions were the same as those in the cases with either UB or US. It seemed that the lift-to-drag ratio was improved by the combined control of UB on the lower surface and US on the upper surface. In particular, the lift-to-drag ratio was most improved by US on the lower rear surface and UB on the upper rear surface.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"212 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128164635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrodynamics and Flow Characterization of Tuna-Inspired Propulsion in Forward Swimming","authors":"Junshi Wang, H. Tran, Martha Christino, C. White, Joseph Zhu, G. Lauder, H. Bart-Smith, Haibo Dong","doi":"10.1115/ajkfluids2019-5472","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5472","url":null,"abstract":"\u0000 A combined experimental and numerical approach is employed to study the hydrodynamic performance and characterize the flow features of thunniform swimming by using a tuna-inspired underwater vehicle in forward swimming. The three-dimensional, time-dependent kinematics of the body-fin system of the underwater vehicle is obtained via a stereo-videographic technique. A high-fidelity computational model is then directly reconstructed based on the experimental data. A sharp-interface immersed-boundary-method (IBM) based incompressible flow solver is employed to compute the flow. The primary objective of the computational effort is to quantify the thrust performance of the model. The body kinematics and hydrodynamic performances are quantified and the dynamics of the vortex wake are analyzed. Results have shown significant leading-edge vortex at the caudal fin and unique vortex ring structures in the wake. The results from this work help to bring insight into understanding the thrust producing mechanism of thunniform swimming and to provide potential suggestions in improving the hydrodynamic performance of swimming underwater vehicles.","PeriodicalId":314304,"journal":{"name":"Volume 1: Fluid Mechanics","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133784156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}