Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl最新文献

{"title":"The Effects of Wakes on Aerodynamic Characteristics of Flapping Wings in Clap-and-Fling Motion at Re of ~104","authors":"Jong-Seob Han, Jae-Hung Han","doi":"10.1115/FEDSM2018-83112","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83112","url":null,"abstract":"In this paper, aerodynamic characteristics of two flapping wings in clap-and-fling motion at Re of ∼104, which corresponds to the flight regime of flapping-wing micro air vehicles, was investigated. The test employing dynamically scaled-up robotic arms installed on a water tank revealed that the wingbeat motion at such high Re in1duced the fully developed wake within two wingbeat cycles. This wake widely influenced the lift production covering the entire wingbeat period; the wings earned the additional lift during the entire downstroke, and lost the lift during the upstroke. Chordwise cross-sectional DPIV showed the massive downwash with enlarged tip vortices, when the wake was fully developed. The wake blew down the headwind and reduced the effective angles of attack. In the case of the clap-and-fling motion, the wake was leaned toward the dorsal part, in which the wings created the clap-and-fling motion, causing the global fluctuation of the aerodynamic force production.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"2013 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76751708","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":"Nucleate Boiling Heat Transfer and Bubble Dynamics of Water-in-Polyalphaolefin Nanoemulsion","authors":"Jiajun Xu, J. McLaurin, Cyree Beckett","doi":"10.1115/FEDSM2018-83397","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83397","url":null,"abstract":"In this study, an experimental study of the nucleation heat transfer and bubble dynamics inside the Water-in-PAO nanoemulsion fluid has been performed. Synchronized highspeed video and infrared thermography are used here to capture time-resolved temperature distribution data for the boiling surface and direct visualization of the bubble cycle. Data gathered included measurements of bubble growth versus time, as well as temperature history of the heater surface underneath the bubbles. Our findings demonstrate a substantial increase in nucleate heat transfer (i.e., heat transfer coefficient), and significantly different bubble dynamics of nanoemulsion fluid compared to pure water. The bubble growth rate of the nanoemulsion lies in the diffusion-controlled regime, and the growth data fit a power law at n ≈ 0.3. This is similar to the authors’ previous study of a similar fluid and is very different from conventional fluids. While the heat transfer mechanisms behind are not completely understood yet, it is hypothesized that the interfacial structures and thermal transport between surfactant molecules surrounding water nanodroplets and the base PAO fluid at elevated temperature may contribute to that.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"423 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77236199","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":"Numerical Analysis of Droplet Impact on a Smooth Slippery Surface","authors":"F. Yeganehdoust, I. Karimfazli, A. Dolatabadi","doi":"10.1115/FEDSM2018-83282","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83282","url":null,"abstract":"Spontaneous bouncing of a droplet that impacts a surface is a mechanism that occurs for the moderate range of droplet impact velocities and is caused by the formation of a stable air layer (cushion) between the droplet and the surface. This bouncing behavior is more pronounced on Lubricant Impregnated Surfaces (LISs) inspired by the natural non-wetting surface of the pitcher plant, which relies on the stable formation of a thin lubricant film across its surface.\u0000 In this study, we performed modeling of the water-oil–air interfacial surfaces using the volume of fluid (VOF) methodology to simulate the impact of a water droplet onto a lubricant smooth surface with an oil as the lubricant. To resolve the effects of the air surrounding the droplet, computational cells were extensively small to capture the presence of the sub-micron layer of air trapped underneath the droplet during the impact.\u0000 The model was able to capture the initiation and subsequent effect of the air cushion on the droplet hydrodynamics. We found that the stability of the air cushion and the impact dynamics are independent of the oil viscosity for specific thicknesses of lubricant layers, whereas the impact conditions such as velocity and droplet properties played a significant role on the outcome of droplet impact. Hence, the dynamics of a droplet falling on a specific thickness of oil film was influenced by the squeezed air trapped between the two immiscible fluid (water and oil). In addition, the formation of high pressure dimple region was evident, which in some cases lead to entrapment of the air bubble. Finally, we validated the results with the existing experimental data in the literature.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80213726","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":"Experimental Study of Flow Around a Rotating Sphere at a Moderate Reynolds Number","authors":"Zhuoyue Li, N. Gao","doi":"10.1115/FEDSM2018-83325","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83325","url":null,"abstract":"Aerodynamic forces on a rotating golf ball were measured in a water tunnel for a Reynolds number of ReD = 8000 at a spinning ratio Vs/Uo (the surface velocity over the freestream velocity) between 0 and 6.0. The flow fields downstream of a spinning sphere were also measured using a time-resolved stereoscopic PIV system with field-of-views perpendicular to the incoming flow to capture the three velocity components.There appeared to be several critical spinning ratios at Vs/Uo ≈ 0.75, 2.0 and 3.0. Both lift and drag increased quickly for Vs/Uo ≲ 0.75; there was a sudden drop in lift at Vs/Uo ≈ 0.75; lift increased quickly while drag increased slowly for 1.0 ≲ Vs/Uo ≲ 2.0; both lift and drag plateaued for 2.0 ≲ Vs/Uo ≲ 3.0; lift increased while drag decreased for large spinning ratios 3.0 ≲ Vs/Uo ≲ 6.0. Flow measurements suggested the lift increase was associated with a downwash downstream of spinning ball. Down wash induced a pair of counter-rotating vortices that caused increases in drag, similar to the induced drag on a finite-span wing. Boundary layer transition occurred on retreating side at a large spinning ratio 3.0 ≲ Vs/Uo ≲ 6.0, the downward appeared to be weaker in this situation and drag increased thus became smaller again.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"166 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77859554","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":"A Comparison of Strong and Weak Coupling Schemes for Computational Aeroelasticity in OpenFOAM","authors":"Sabet Seraj, A. Fereidooni, A. Grewal","doi":"10.1115/FEDSM2018-83292","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83292","url":null,"abstract":"Two coupling schemes for fluid-structure interaction using the OpenFOAM structural solver sixDoF Rigid Body Motion are developed. The first scheme is developed by modifying the baseline leapfrog weak coupling scheme to minimize the lag between the fluid and structural solvers. The second is a strong coupling scheme based on the Crank-Nicolson method. The two newly implemented schemes and the baseline are compared through the aeroelastic simulation of a NACA 64A010 airfoil and the Benchmark Supercritical Wing. The aeroelastic solutions obtained using the newly implemented schemes exhibit significantly lower sensitivity to changes in time step size compared to the baseline weak coupling scheme. The modified weak coupling and strong coupling schemes perform comparably for the cases studied.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90816387","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":"Modeling of Decelerated Descent of an Elongated Body With Vectored Thrust","authors":"K. Matveev, J. Swensen, Matthew E. Taylor","doi":"10.1115/FEDSM2018-83171","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83171","url":null,"abstract":"The subject of this study is a simplified model of an elongated body intended for controlled, low-speed landing after being released far above the ground. The envisioned system is structurally simple and compact. It comprises a cylindrical body with a vectored propulsor attached to its upper end. Far from the ground a low-magnitude thrust force directs the body toward the target site and maintains stable orientation, whereas near the ground higher thrust decelerates and directs the body to ensure low-speed landing near the target location. A 6-DOF dynamics model is applied for simulating the body descent. A strip approach is used for evaluating aerodynamic forces on the body. The thrust magnitude and direction are the controlled parameters. Results of simulations are presented for several scenarios of the body descending on the ground in calm air and in the presence of wind.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87126167","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":"Three-Dimensional Volume of Fluid Simulations of Air Bubble Dynamics in a Converging Nozzle","authors":"D. Law, Thomas G. Shepard","doi":"10.1115/FEDSM2018-83180","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83180","url":null,"abstract":"The present work relates to the dynamics of single bubbles accelerating through a converging nozzle. There are two main aspects to this study. First, this expands upon a previously used two-dimensional model [1] by providing three-dimensional volume of fluid (VOF) simulations that show better agreement with experiments. The VOF model is employed to perform simulations using the commercial computational fluid dynamics (CFD) code ANSYS FLUENT. Second, the present work uses experimental high-speed camera results in conjunction with simulation results to demonstrate bubble time trace and velocity information. Time series of the average liquid velocity at the atomizer exit orifice when the bubble exits as determined via simulation are reported. The passing of a bubble through the nozzle is found to cause a significant fluctuation in the exit velocity that is coupled to the liquid and gas dynamics upstream of the exit.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87606679","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":"Internal Groove Influenced Thermohydraulic Performance on an Air-Channel","authors":"G. I. Mahmood, Aasa Samson","doi":"10.1115/FEDSM2018-83236","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83236","url":null,"abstract":"Internal fins, protrusions, and porous foams enhance the local convective heat transfer at the channel walls in the heat exchangers, electronic chips for cooling, and solar panels for cooling and heating by promoting the local turbulence in flow. However, the fluid pumping power in the channel suffers due to the blockage and high pressure drop caused by the fins, protrusions, and foams. The present article reports the experimental friction factors and Nusselt numbers in a rectangular channel with an array of internal grooves in one wall. The grooves provide the minimum flow blockage, but still promote the local turbulence to enhance the surface heat transfer. The cylindrical grooves are machined at 45° to the mean air-flow direction in one of the wide walls of the channel of aspect ratio of 40.6:1. The ratio of groove print-diameter to depth is 2.83:1. The objectives are to investigate the effects of groove pitch on the thermal performance in the channel as the flow Reynolds number (Re) varies between 600 and 15000. Two ratios of groove-pitch to print-diameter are employed — 3.2:1 and 4.5:1. The measurements include the distributions of the wall staticpressure and heat transfer coefficient along the channel wall having the grooves. The pressure distributions are obtained at the adiabatic condition. The heat transfer coefficients are obtained with the constant heat flux boundary condition from the grooved surface. The measurements are also obtained in the smooth channel when the grooved wall is replaced by a smooth wall for comparisons with the grooved channel. The results indicate the ratio of Darcy friction factor (f/fo) for the grooved channel (f) to that for the smooth channel (fo) increases with the Re by 27% and 41% at the maximum for the two grooves. The f/fo ratios are slightly higher for the grooves with the smaller pitch. The fully developed Nusselt number ratio (Nu/Nuo) for the grooved channel (Nu) to that for the smooth channel (Nuo) increases with the Re by 37% at the maximum for the two grooves. However, the thermal performance quantified by the ratio (Nu/Nuo)/(f/fo)1/3 is higher for the smaller pitch grooves for most of the Reynolds numbers > 2000. The results thus contribute to the design of heat exchangers and cooling channels for high thermal performance with the ratio (Nu/Nuo)/(f/fo)1/3 > 1.0 based on the smaller surface area, pumping power, and heat duty.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82411474","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":"Force Production Mechanisms of a Heaving and Pitching Foil Operating in the Energy Harvesting Regime","authors":"Firas F. Siala, M. Prier, J. Liburdy","doi":"10.1115/FEDSM2018-83111","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83111","url":null,"abstract":"The influence of vortex dynamics on the force production of a heaving and pitching foil operating in the energy harvesting regime is studied experimentally using 2C-PIV. Results are obtained for reduced frequencies in the range of k = fc/U = 0.06 to 0.14. The flow induced vertical force-time history during cyclic operation is evaluated from PIV data by using the impulse-based derivative moment transformation method. The contribution of each term in the equation is investigated. The results show that the leading edge vortex has the largest contribution to the total force, whereas the trailing edge vortex is shown to contribute negatively. In addition, the dynamics of the leading edge vortex are further analyzed by measuring the circulation and trajectory relative to the foil. It is shown that the force is not only dependent on the circulation magnitude, but also on the LEV foil-normal and chord-wise trajectories. The force-time history for all reduced frequencies exhibit two main distinct peaks. The primary peak is generated when the leading edge vortex forms. The secondary peak, on the other hand, is formed when the chord-wise convection of the leading edge vortex increases, as well as when the LEV is closer to the foil surface during the reversal of pitching motion.","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75399710","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":"Evaluation of Models for Droplet Shear Effect of Centrifugal Pump","authors":"Ramin Dabirian, S. Cui, I. Gavrielatos, R. Mohan, O. Shoham","doi":"10.1115/FEDSM2018-83318","DOIUrl":"https://doi.org/10.1115/FEDSM2018-83318","url":null,"abstract":"During the process of petroleum production and transportation, equipment such as pumps and chokes will cause shear effects which break the dispersed droplets into smaller size. The smaller droplets will influence the separator process significantly and the droplet size distribution has become a critical criterion for separator design. In order to have a better understanding of the separation efficiency, estimation of the dispersed-phase droplet size distribution is very important. The objective of this paper is to qualitatively and quantitatively investigate the effect of shear imparted on oil-water flow by centrifugal pump.\u0000 This paper presents available published models for the calculation of droplet size distribution caused by different production equipment. Also detailed experimental data for droplet size distribution downstream of a centrifugal pump are presented. Rosin-Rammler and Log-Normal Distributions utilizing dmax Pereyra (2011) model as well as dmin Kouba (2003) model are used in order to evaluate the best fit distribution function to simulate the cumulative droplet size distribution. The results confirm that applying dmax Pereyra (2011) model leads to Rosin-Rammler distribution is much closer to the experimental data for low shear conditions, while the Log-Normal distribution shows better performance for higher shear rates. Furthermore, the predictions of Modified Kouba (2003) dmin model show good results for predicting the droplet distribution in centrifugal pump, and even better predictions under various ranges of experiments are achieved with manipulating cumulative percentage at minimum droplet diameter F(Dmin).","PeriodicalId":23480,"journal":{"name":"Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fl","volume":"177 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76931359","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}