A Contribution to Study on the Lift of Ventilated Supercavitating Vehicle With Low Froude Number

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Yu Kaiping ◽  
Zhou Jingjun ◽  
Min Jingxin ◽  
Zhang Guang
Keyword(s):  
Numerical Simulations ◽  
Froude Number ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Gravitational Effect ◽  
Gas Leakage ◽  
Supercavitating Vehicle ◽  
Numerical Predictions ◽  
Low Froude Number

A ventilated cavity was investigated using three-dimensional numerical simulation and cavitation water tunnel experiments under the condition of low Froude number. A two-fluid multiphase flow model was adopted in numerical predictions. The drag between the different phases and gravitational effect, as well as the compressibility of gas, was considered in the numerical simulations. By comparing the ventilated coefficient computational results of three different turbulence models with the Epshtein formula, the shear-stress-transport turbulence model was finally employed. The phenomenon of double-vortex tube gas-leakage was observed in both numerical simulations and experiments. Based on the validity of the numerical method, the change law of the lift coefficient on the afterbody was given by numerical predictions and accorded well with experimental results. The cause for the appearance of an abrupt increase in lift was difficult to get from experiments for the hard measurement, whereas the numerical simulations provided some supplements to analyze the reasons. The distribution of lift coefficient on the afterbody had important significance to the design of underwater vehicles.

Computational Investigation of Torque on Coaxial Rotating Cones

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Steve Rapley ◽  
Carol Eastwick ◽  
Kathy Simmons
Keyword(s):  
Three Dimensional ◽  
Turbulence Models ◽  
Frictional Resistance ◽  
Vertex Angle ◽  
Numerical Predictions ◽  
Rotating Cone ◽  
Taylor Couette ◽  
Dimensional Models ◽  
Three Dimensional Models ◽  
Cone Vertex

This article looks at a modification of Taylor–Couette flow, presenting a numerical investigation of the flow around a shrouded rotating cone, with and without throughflow, using the commercial computational fluid dynamics code FLUENT 6.2 and FLUENT 6.3. The effects of varying the cone vertex angle and the gap width on the torque seen by the rotating cone are considered, as well as the effect of a forced throughflow. The performance of various turbulence models are considered, as well as the ability of common wall treatments/functions to capture the near-wall behavior. Close agreement is found between the numerical predictions and previous experimental work, carried out by Yamada and Ito (1979, “Frictional Resistance of Enclosed Rotating Cones With Superposed Throughflow,” ASME J. Fluids Eng., 101, pp. 259–264; 1975, “On the Frictional Resistance of Enclosed Rotating Cones (1st Report, Frictional Moment and Observation of Flow With a Smooth Surface),” Bull. JSME, 18, pp. 1026–1034; 1976, “On the Frictional Resistance of Enclosed Rotating Cones (2nd Report, Effects of Surface Roughness),” Bull. JSME, 19, pp. 943–950). Limitations in the models are considered, and comparisons between two-dimensional axisymmetric models and three-dimensional models are made, with the three-dimensional models showing greater accuracy. The work leads to a methodology for modeling similar flow conditions to Taylor–Couette.

Performance evaluation by computational fluid dynamics modelling of the heavy gas dispersion with a low Froude number in a built environment

2019 ◽  
Vol 29 (5) ◽  
pp. 656-670 ◽  
Author(s):  
Ying Zhang ◽  
Longtao Wang ◽  
Angui Li ◽  
Pengfei Tao
Keyword(s):  
Built Environment ◽  
Froude Number ◽  
Geometric Mean ◽  
Model Performance ◽  
Turbulence Models ◽  
Experimental Chamber ◽  
Gas Dispersion ◽  
Low Froude Number ◽  
Dynamics Modelling ◽  
Heavy Gas

To evaluate the dispersion of a heavy gas, such as sulphur hexafluoride, with a low Froude number in a built environment, an experimental and numerical simulation study was conducted. The experiment was carried out using seven different injection inlet configurations in an experimental chamber. The release rate was found to have a great effect on the concentration in the lower part of the chamber. The obstacle in the middle of the chamber could cause a non-uniform distribution of concentration, particularly due to variations in locations and angles of the release outlets. Additionally, numerical simulations were carried out to evaluate four turbulence models: the standard k- ε model, the realizable k- ε model, the re-normalization group (RNG) k- ε model and the shear stress transport (SST) k-ω model. Four indicators were used to evaluate the turbulent model performance. In general, the SST k-ω model performed the best, with geometric mean bias ( MG) = 0.968 and geometric variance ( VG) = 1.09 at 0.055 m height, and with MG = 0.384 and VG = 2.80 at 0.6 m height. The standard k- ε model was the next best in performance, followed by the realizable k- ε and the RNG k- ε model.

Numerical simulations of the flow through the inlet and isolator of a Mach 4 dual mode scramjet

2012 ◽  
Vol 116 (1182) ◽  
pp. 833-846 ◽  
Author(s):  
S. Janarthanam ◽  
V. Babu
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Dual Mode ◽  
Flow Distortion ◽  
Capture Ratio ◽  
Boundary Interaction ◽  
Numerical Predictions ◽  
Mass Capture

Abstract Results from numerical simulations of the three dimensional flow in the intake-isolator of a dual mode scramjet are presented. The FANS calculations have utilised the SST k -ω turbulence model. The effect of cowl length and cowl convergence angle on the inlet mass capture ratio, flow distortion, shock strength and pressure rise are studied in detail. Three cowl lengths and four or five cowl convergence angles for each cowl length are considered. The predicted values of the dimensionless wall static pressure and inlet mass capture ratio are compared with experimental data reported in the literature. The numerical predictions are shown to agree well with the experimental data. In addition, details of the flow field such as shocks, expansion fans and shock boundary interaction are also captured accurately. Inlet unstart is also demonstrated for one case.

Study of Turbulence Models in Flows Through Adverse Pressure Gradient System

2005 ◽  
Author(s):  
E. Karunakaran ◽  
V. Ganesan
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Pressure Gradient ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Adverse Pressure Gradient ◽  
Reynolds Stress Model ◽  
Gradient System ◽  
Field Development

This paper is concerned with the study of performance of popular turbulence models used in the CFD analysis. Turbulence models considered for evaluation include the eddy viscosity models and the Reynolds stress model. The recent k-ε-v2-f model recommended for a flow with separation is also studied. Evaluation of the turbulence models in the present study focuses on a three-dimensional flow field development with adverse pressure gradient and flows that simulate wall-bounded turbulence. Numerical calculations are performed using SIMPLE based algorithm. Nowadays, decelerating flow in a diffuser is assessed by numerical simulations and the validation is done with experimental results. A comparison of the numerical results and the experimental data are presented. The main objective of the comparison is to obtain information on how well the numerical simulations representing the flow field with the standard turbulence models, are able to reproduce the experimental data.

scholarly journals Numerical Prediction of Three-Dimensional Flows in a Double-Recirculating Combustor

1985 ◽  
Author(s):  
Y. Wang ◽  
B. Q. Zhang
Keyword(s):  
Boundary Conditions ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Numerical Prediction ◽  
Implicit Method ◽  
Different Boundary Conditions ◽  
Numerical Predictions

The SIMPLE (for Semi-Implicit Method for Pressure-Linked Equations) is successfully used in predicting three-dimensional flows in a double-recirculating combustor. Effects of different boundary conditions and turbulence models on the flow are examined. Compared with experiment results, the numerical predictions are satisfactory.

Numerical and Experimental Study of a Ventilated Supercavitating Vehicle

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
I. Rashidi ◽  
Ma. Pasandideh-Fard ◽  
Mo. Passandideh-Fard ◽  
N. M. Nouri
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Surface Treatment ◽  
Numerical Simulations ◽  
The Other ◽  
Water Tunnel ◽  
Cavity Shape ◽  
Gas Leakage ◽  
Supercavitating Vehicle ◽  
Air Ventilation

In this paper, the ventilated supercavities are studied both numerically and experimentally. A slender rod is considered as the solid body which has a sharp edged disk at the nose as a cavitator and special ports for air ventilation. The experiments are conducted in a recirculating water tunnel. The simulations are provided for two different algorithms in free-surface treatment, both using the VOF method but one using Youngs' algorithm in the advection of the free-surface and the other without. The comparison between numerical simulations and experiments show that the numerical method using Youngs' algorithm accurately simulates the physics of ventilated cavitation phenomena such as the cavity shape, the gas leakage and the re-entrant jet.

Numerical Simulation on Ventilated Cavity Flow with Different Turbulence Models

2013 ◽  
Vol 368-370 ◽  
pp. 544-548 ◽  
Author(s):  
Xiao Hu ◽  
Yong Liang Xiong
Keyword(s):  
Three Dimensional ◽  
Turbulence Models ◽  
Cavity Flow ◽  
Cavity Shape ◽  
Gas Leakage ◽  
Eddy Simulation ◽  
Ventilated Cavity ◽  
Tail Part ◽  
Turbulent Models ◽  
The Impact

The gas leakage and capabilities in cavity tail-part can affect the characteristics of ventilated cavity shape, while turbulence models influence directly the function of turbulence and gas-leakage mode in cavity tail-part. To compare the impact of two turbulent models (large eddy simulation (LES) and Renormalization Group (RNG) k-ε) on ventilated cavity shape, FLUENT6.2 software was used to simulate the three-dimensional ventilated cavity flow, taking into account gravity effects, the cavity transient image and pressure distributions along model surface under two turbulence models were also presented. The results show that the results of LES are more consistent with the transient characteristics of ventilated cavity, and are more suitable for simulations of ventilated cavity flow than RNG k-ε model.

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