Three-Dimensional Two-Phase Flow Simulations of Water Braking Phenomena for High-Speed Test Track Sled

2021 ◽  
Author(s):  
Jose Terrazas ◽  
Arturo Rodriguez ◽  
Vinod Kumar ◽  
Richard Adansi ◽  
V. M. Krushnarao Kotteda
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Initial Boundary ◽  
Phase Flow ◽  
Momentum Exchange ◽  
Two Phase ◽  
Test Track ◽  
Speed Test ◽  
Liquid Phases ◽  
Multi Phase Flow

Abstract Specializing in high-speed testing, Holloman High-Speed Test Track (HHSTT) uses a process called ‘water braking’ as a method to bring vehicles at the test track to a stop. This method takes advantage of the higher density of water, compared to air, to increase braking capability through momentum exchange. By studying water braking using Computational Fluid Dynamics (CFD), forces acting on track vehicles can be approximated and prepared for prior to actual test. In this study, focus will be made on the brake component of the track sled that is responsible for interacting with the water for braking. By discretizing a volume space around our brake, we accelerate water and air to relatively simulate the brake engaging. The model is a multi-phase flow that uses the governing equations of gas and liquid phases with the finite volume method, to perform 3D simulations. By adjusting the inflow velocity of air and water, it is possible to simulate HHSTT sled tests at various operational speeds. In the development of the 3D predictive model, convergence issues associated with the numerical mesh, initial/boundary conditions, and compressibility of the fluids were encountered. Once resolved, the effect of inflow velocities of water and air on the braking of the sled are studied.

Modeling of Multi-Phase Flow in Electro-Chemical Machining: One-Way Coupling Versus Two-Way Coupling

2007 ◽  
Author(s):  
Ryo Tsuboi ◽  
Kazuaki Inaba ◽  
Makoto Yamamoto ◽  
Dai Kato
Keyword(s):  
Coupling Method ◽  
Phase Flow ◽  
Complex Flow ◽  
Two Phase ◽  
Numerical Result ◽  
Liquid Phases ◽  
Hydrogen Bubbles ◽  
Advanced Machining ◽  
Multi Phase Flow ◽  
Channel Configuration

Electro-Chemical Machining (ECM) is an advanced machining technology. It has been applied to highly specialized fields such as aerospace, aeronautics and medical industries. However, it still has some problems to be overcome. The efficient tool-design, electrolyte processing, and disposal of metal hydroxide sludge are the typical issues. To solve such problems, CFD is considered to be a powerful tool in the near future. However, the numerical method that can satisfactorily predict ECM process has not been established because of the complex flow natures. In the present study, we investigate the modeling of the two-phase flow (i.e. fluid and hydrogen bubbles) in ECM process. First, we present two models to calculate flow fields in ECM process. One is based on one-way coupling method, neglecting the effect from gas-phase to liquid-phase. The other takes account of the interaction between gas and liquid phases, namely two-way coupling method. In the later method, assuming that electrolyte and hydrogen bubbles have same velocity, we simplified the governing equations with Low Mach number approximation. We simulated ECM process for a flat plate channel configuration. And, we verified the present models by comparing the numerical result with the experimental data.

The CFD Modeling of the Water Braking Phenomena for the Holloman High-Speed Test Track

2019 ◽  
Author(s):  
Jose Terrazas ◽  
V. M. Krushnarao Kotteda ◽  
Vinod Kumar ◽  
Robert Edmonds ◽  
Michelle Zeisset
Keyword(s):  
High Speed ◽  
Force Balance ◽  
Cfd Modeling ◽  
Critical Infrastructures ◽  
Momentum Exchange ◽  
Test Track ◽  
Speed Test ◽  
High Speeds ◽  
Time Test ◽  
Very High

Abstract 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.

Numerical Simulation and Experimental Validation of Three-Dimensional Unsteady Multi-Phase Flow in Flushing Process of Toilets

2013 ◽  
Vol 444-445 ◽  
pp. 304-311 ◽  
Author(s):  
Jian Guo Hu ◽  
You Song Sun ◽  
Zheng Rong Zhang
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
High Viscosity ◽  
Coupling Scheme ◽  
Phase Flow ◽  
Two Phase ◽  
Discrete Equations ◽  
Vof Model ◽  
Multi Phase Flow ◽  
Multi Phase

In order to predict the flush performances of digital toilet products before mass production, a numerical simulation for a three-dimensional unsteady multi-phase flow in the flushing process of a wash-down toilet is carried out by using FLUENT software. The finite volume method (FVM) is used to discrete the three governing equations in space and time. The discrete equations are solved by using the first-order upwind discretization scheme and the PISO pressure-velocity coupling scheme. The realizable turbulence model is chosen as the viscous model to treat the fluid flow with large bending curvature wall. The volume of fluid (VOF) model is applied to solve the transient free-surface problem. First, a two-phase flow was simulated on the assumption that there is not sewage but water in the trap seal. Then, by simplifying the mixture of sewage and water in the trap seal as the third phase with high viscosity, a three-phase flow was simulated. Moreover, in order to validate the simulated results, a flushing testing was conducted to test the flush range, and a target type flow meter was designed, calibrated and applied to test the flush velocity. The comparisons show a good agreement between the numerical and experimental results. Based on the verified simulation results, the flush performances of the digital wash-down toilet, such as flush range, flush velocity and sewage replacement ability, can be predicted and evaluated.

Development and Validation of a Three-Dimensional Multiphase Flow CFD Analysis for Journal Bearings in Steam and Heavy Duty Gas Turbines

2012 ◽  
Author(s):  
Stephan Uhkoetter ◽  
Stefan aus der Wiesche ◽  
Michael Kursch ◽  
Christian Beck
Keyword(s):  
Experimental Data ◽  
Multiphase Flow ◽  
Gas Turbines ◽  
High Speed ◽  
Three Dimensional ◽  
Air Entrainment ◽  
Journal Bearings ◽  
Heavy Duty ◽  
Present Contribution ◽  
Two Phase

The traditional method for hydrodynamic journal bearing analysis usually applies the lubrication theory based on the Reynolds equation and suitable empirical modifications to cover turbulence, heat transfer, and cavitation. In cases of complex bearing geometries for steam and heavy-duty gas turbines this approach has its obvious restrictions in regard to detail flow recirculation, mixing, mass balance, and filling level phenomena. These limitations could be circumvented by applying a computational fluid dynamics (CFD) approach resting closer to the fundamental physical laws. The present contribution reports about the state of the art of such a fully three-dimensional multiphase-flow CFD approach including cavitation and air entrainment for high-speed turbo-machinery journal bearings. It has been developed and validated using experimental data. Due to the high ambient shear rates in bearings, the multiphase-flow model for journal bearings requires substantial modifications in comparison to common two-phase flow simulations. Based on experimental data, it is found, that particular cavitation phenomena are essential for the understanding of steam and heavy-duty type gas turbine journal bearings.

Age-Related Differences in Throwing Techniques Used by the Catcher in Baseball

1994 ◽  
Vol 6 (3) ◽  
pp. 225-235 ◽  
Author(s):  
Shinji Sakurai ◽  
Bruce Elliott ◽  
J. Robert Grove
Keyword(s):  
High Speed ◽  
High Performance ◽  
Age Groups ◽  
Three Dimensional ◽  
Transformation Method ◽  
High Speed Photography ◽  
Two Phase ◽  
Ball Speed ◽  
Age Related ◽  
Release Speed

Three-dimensional (3-D) high speed photography was used to record the overarm throwing actions of five open-age, four 18-year-old, six 16-year- old, and six 14-year-old high-performance baseball catchers. The direct linear transformation method was used for 3-D space reconstruction from 2-D images of the catchers throwing from home plate to second base recorded using two phase-locked cameras operating at a nominal rate of 200 Hz. Selected physical capacity measures were also recorded and correlated with ball release speed. In general, anthropometric and strength measures significantly increased through the 14-year-old to open-age classifications, while a range of correlation coefficients from .50 to .84 was recorded between these physical capacities and ball speed at release. While many aspects of the kinematic data at release were similar, the key factors of release angle and release speed varied for the different age groups.

High Speed Imaging and Two-Phase Flow Patterns During Flow Boiling in a Single Microchannel

2008 ◽  
Author(s):  
Jacqueline Barber ◽  
Khellil Sefiane ◽  
David Brutin ◽  
Lounes Tadrist
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Pressure Sensors ◽  
Flow Patterns ◽  
Bubble Nucleation ◽  
Phase Flow ◽  
Vapour Bubble ◽  
Two Phase ◽  
Over Time

Boiling in microchannels remains elusive due to the lack of full understanding of the mechanisms involved. A powerful tool in achieving better comprehension of the mechanisms is detailed imaging and analysis of the two phase flow at a fundamental level. We induced boiling in a single microchannel geometry (hydraulic diameter 727 μm), using a refrigerant FC-72, to investigate several flow patterns. A transparent, metallic, conductive deposit has been developed on the exterior of rectangular microchannels, allowing simultaneous uniform heating and visualisation to be conducted. The data presented in this paper is for a particular case with a uniform heat flux of 4.26 kW/m2 applied to the microchannel and inlet liquid mass flowrate, held constant at 1.33×10−5 kg/s. In conjunction with obtaining high-speed images and videos, sensitive pressure sensors are used to record the pressure drop profiles across the microchannel over time. Bubble nucleation, growth and coalescence, as well as periodic slug flow, are observed in the test section. Phenomena are noted, such as the aspect ratio and Reynolds number of a vapour bubble, which are in turn correlated to the associated pressure drops over time. From analysis of our results, images and video sequences with the corresponding physical data obtained, it is possible to follow visually the nucleation and subsequent both ‘free’ and ‘confined’ growth of a vapour bubble over time.

A Combined Eulerian and Lagrangian Method for Prediction of Evaporating Sprays

2002 ◽  
Vol 124 (3) ◽  
pp. 481-488 ◽  
Author(s):  
M. Burger ◽  
G. Klose ◽  
G. Rottenkolber ◽  
R. Schmehl ◽  
D. Giebert ◽  
...  
Keyword(s):  
Two Phase Flow ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Lagrangian Method ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Two Phase ◽  
Lagrangian Methods ◽  
Eulerian Method ◽  
Lagrangian Modeling

Polydisperse sprays in complex three-dimensional flow systems are important in many technical applications. Numerical descriptions of sprays are used to achieve a fast and accurate prediction of complex two-phase flows. The Eulerian and Lagrangian methods are two essentially different approaches for the modeling of disperse two-phase flows. Both methods have been implemented into the same computational fluid dynamics package which is based on a three-dimensional body-fitted finite volume method. Considering sprays represented by a small number of droplet starting conditions, the Eulerian method is clearly superior in terms of computational efficiency. However, with respect to complex polydisperse sprays, the Lagrangian technique gives a higher accuracy. In addition, Lagrangian modeling of secondary effects such as spray-wall interaction enhances the physical description of the two-phase flow. Therefore, in the present approach the Eulerian and the Lagrangian methods have been combined in a hybrid method. The Eulerian method is used to determine a preliminary solution of the two-phase flow field. Subsequently, the Lagrangian method is employed to improve the accuracy of the first solution using detailed sets of initial conditions. Consequently, this combined approach improves the overall convergence behavior of the simulation. In the final section, the advantages of each method are discussed when predicting an evaporating spray in an intake manifold of an internal combustion engine.

scholarly journals Numerical Simulation and Analysis on Spray Drift Movement of Multirotor Plant Protection Unmanned Aerial Vehicle

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2399 ◽  
Author(s):  
Fengbo Yang ◽  
Xinyu Xue ◽  
Chen Cai ◽  
Zhu Sun ◽  
Qingqing Zhou
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Droplet Size ◽  
Wind Field ◽  
Flow Model ◽  
Two Phase Flow ◽  
Plant Protection ◽  
Three Dimensional ◽  
Phase Flow ◽  
Two Phase

In recent years, multirotor unmanned aerial vehicles (UAVs) have become more and more important in the field of plant protection in China. Multirotor unmanned plant protection UAVs have been widely used in vast plains, hills, mountains, and other regions, and become an integral part of China’s agricultural mechanization and modernization. The easy takeoff and landing performances of UAVs are urgently required for timely and effective spraying, especially in dispersed plots and hilly mountains. However, the unclearness of wind field distribution leads to more serious droplet drift problems. The drift and distribution of droplets, which depend on airflow distribution characteristics of UAVs and the droplet size of the nozzle, are directly related to the control effect of pesticide and crop growth in different growth periods. This paper proposes an approach to research the influence of the downwash and windward airflow on the motion distribution of droplet group for the SLK-5 six-rotor plant protection UAV. At first, based on the Navier-Stokes (N-S) equation and SST k–ε turbulence model, the three-dimensional wind field numerical model is established for a six-rotor plant protection UAV under 3 kg load condition. Droplet discrete phase is added to N-S equation, the momentum and energy equations are also corrected for continuous phase to establish a two-phase flow model, and a three-dimensional two-phase flow model is finally established for the six-rotor plant protection UAV. By comparing with the experiment, this paper verifies the feasibility and accuracy of a computational fluid dynamics (CFD) method in the calculation of wind field and spraying two-phase flow field. Analyses are carried out through the combination of computational fluid dynamics and radial basis neural network, and this paper, finally, discusses the influence of windward airflow and droplet size on the movement of droplet groups.

Analysis of Transient Two-Phase Flow in Pressure Safety Valve Outlet Headers

2018 ◽  
Author(s):  
Maral Taghva ◽  
Lars Damkilde
Keyword(s):  
Steady State ◽  
Shock Waves ◽  
High Speed ◽  
Two Phase Flow ◽  
Safety Valve ◽  
Strong Shock ◽  
Flow Property ◽  
Phase Flow ◽  
Transient Pressure ◽  
Two Phase

To protect a pressurized system from overpressure, one of the most established strategies is to install a Pressure Safety Valve (PSV). Therefore, the excess pressure of the system is relieved through a vent pipe when PSV opens. The vent pipe is also called “PSV Outlet Header”. After the process starts, a transient two-phase flow is formed inside the outlet header consisting of high speed pressurized gas interacting with existing static air. The high-speed jet compresses the static air towards the end tail of the pipe until it is discharged to the ambiance and eventually, the steady state is achieved. Here, this transient process is investigated both analytically and numerically using the method of characteristics. Riemann’s solvers and Godunov’s method are utilized to establish the solution. Propagation of shock waves and flow property alterations are clearly demonstrated throughout the simulations. The results show strong shock waves as well as high transient pressure take place inside the outlet header. This is particularly important since it indicates the significance of accounting for shock waves and transient pressure, in contrast to commonly accepted steady state calculations. More precisely, shock waves and transient pressure could lead to failure, if the pipe thickness is chosen only based on conventional steady state calculations.

Sign in / Sign up

Export Citation Format

Share Document