An Efficient Shock-Capturing Scheme for Simulating Compressible Homogeneous Mixture Flow

2015 ◽  
Author(s):  
Son-Tung Dang ◽  
Cong-Tu Ha ◽  
Warn Gyu Park ◽  
Chul-Min Jung
Keyword(s):  
Numerical Results ◽  
Homogeneous Mixture ◽  
Shock Capturing ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Mixture Flow ◽  
Wide Range ◽  
Homogeneous Mixture Model ◽  
Accurate Computations ◽  
Good Agreement

In this paper, we focus on using high-resolution implicit upwind shock-capturing scheme to avoid the formation of non-linear instabilities and numerical oscillations across shock waves or discontinuities. The governing equation is the compressible Reynolds Averaged Navier-Stokes equation based on the homogeneous mixture model. A preconditioned method is applied for enhancing efficient and accurate computations over a wide range of Mach numbers. For evaluation, the results from the present study have been compared with experiments and other numerical results. A fairly good agreement with the experimental data and other numerical results have been obtained. Finally, the simulation of ventilated supercavitating flows over a torpedo with a hot propulsive jet was conducted to verify the efficiency of numerical scheme.

Method for Non-Dimensional Tip Leakage Flow Characterization in Radial Turbines

2018 ◽  
Author(s):  
José Ramón Serrano ◽  
Roberto Navarro ◽  
Luis Miguel García-Cuevas ◽  
Lukas Benjamin Inhestern
Keyword(s):  
Suction Side ◽  
Tip Clearance ◽  
Navier Stokes ◽  
The Novel ◽  
Tip Leakage Flow ◽  
Navier Stokes Equation ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Wide Range ◽  
Clearance Flow

Tip leakage loss characterization and modeling plays an important role in small size radial turbine research. The momentum of the flow passing through the tip gap is highly related with the tip leakage losses. The ratio of fluid momentum driven by the pressure gradient between suction side and pressure side and the fluid momentum caused by the shroud friction has been widely used to analyze and to compare different sized tip clearances. However, the commonly used number for building this momentum ratio lacks some variables, as the blade tip geometry data and the viscosity of the used fluid. To allow the comparison between different sized turbocharger turbine tip gaps, work has been put into finding a consistent characterization of radial tip clearance flow. Therefore, a non-dimensional number has been derived from the Navier Stokes Equation. This number can be calculated like the original ratio over the chord length. Using the results of wide range CFD data, the novel tip leakage number has been compared with the traditional and widely used ratio. Furthermore, the novel tip leakage number can be separated into three different non-dimensional factors. First, a factor dependent on the radial dimensions of the tip gap has been found. Second, a factor defined by the viscosity, the blade loading, and the tip width has been identified. Finally, a factor that defines the coupling between both flow phenomena. These factors can further be used to filter the tip gap flow, obtained by CFD, with the influence of friction driven and pressure driven momentum flow.

scholarly journals Numerical Analysis of Multi-Phase Flow around Supercavitating Body at Various Cavitator Angle of Attack and Ventilation Mass Flux

2020 ◽  
Vol 10 (12) ◽  
pp. 4228
Author(s):  
Dong-Hyun Kim ◽  
SalaiSargunan S Paramanantham ◽  
Warn-Gyu Park
Keyword(s):  
Flow Analysis ◽  
Angle Of Attack ◽  
Homogeneous Mixture ◽  
Navier Stokes ◽  
Cavitation Flow ◽  
Navier Stokes Equation ◽  
Gas Phases ◽  
Continuity Equations ◽  
Mixture Phase ◽  
Multi Phase Flow

Cavitation flow is an important issue in many areas of mechanical engineering. In this study, the natural and ventilated cavitation analyses were performed using the developed code for the cavitation flow analysis. The governing equation is the Navier-Stokes equation based on a homogeneous mixture model. This model assumes that all fluids are in an equilibrium state of momentum. The momentum equations are solved using the homogeneous mixture phase, although the continuity equations are solved in the liquid, vapor, and gas phases, separately. Computational analysis was performed for the different injection conditions and inflow velocity conditions under the same conditions as the experiments. The comparison between the cavitation shape and the drag showed good agreement with the experiments. Based on this, this study predicted the change of cavitation shape according to the change of cavitator angle of attack.

Flow resistance of ice-covered streams

1984 ◽  
Vol 11 (4) ◽  
pp. 815-823 ◽  
Author(s):  
S. P. Chee ◽  
M. R. I. Haggag
Keyword(s):  
Velocity Profile ◽  
Channel Flow ◽  
Flow Resistance ◽  
Ice Cover ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Cross Sectional ◽  
Roughness Elements ◽  
Mixing Length Theory ◽  
Good Agreement

This paper deals with the underlying theory of the hydraulics of channel flow with a buoyant boundary as an ice cover. It commences by developing the velocity distribution in two-dimensional covered channel flow using the Reynolds form of the Navier–Stokes equation in conjunction with the Prandtl – Von Karman mixing length theory. Central to the theory is the division of the channel into two subsections. From the developed velocity profile, the functional relationship for the division surface is obtained. Finally, the composite roughness of the channel is derived.Experimental verification of the developed theory was conducted in laboratory flumes. Seven cross-sectional shapes were utilized. Ice covers were simulated with polyethylene plastic pellets as well as floating plywood boards with roughness elements attached to the underside. Velocity profile and composite roughness measurements made in these flumes were in good agreement with the theoretical equations. The composite roughness relationship derived from the theory is very comprehensive, as it takes into account not only the varying rugosities of the channel and its floating boundary but also the shape of the cross section. Key words: composite roughness, ice cover, flow resistance, velocity profile, buoyant boundary, covered channel.

scholarly journals Aerodynamic Performances of Paper Planes

2020 ◽  
Vol 77 (1) ◽  
pp. 124-131
Author(s):  
Noor Iswadi Ismail ◽  
Zurriati Mohd Ali ◽  
Iskandar Shah Ishak ◽  
R.M. Noor ◽  
Rosniza Rabilah
Keyword(s):  
Lift Coefficient ◽  
The Other ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Aerodynamic Efficiency ◽  
Ansys Cfx ◽  
Wide Range ◽  
Aerodynamic Performances ◽  
Paper Plane ◽  
Stall Angle

Paper plane has a high potential to be upgraded as a Micro Air Vehicle (MAV). Due to its simplicity, paper plane offers easier design option compared to the biological inspired designs as shown in recent MAV development. However, researchers have underestimate and overlook the basic aerodynamic performance induced by these paper planes. This is due to its common usage as toys and wide range of paper plane design. Thus, the objective for current work is to analyse and compare the aerodynamics forces and its performance for selected paper plane design known as Glider, Wide Stunt Glider Plane and Stunt plane. A series of CFD simulations on each paper plane was executed by using ANSYS-CFX module. A steady state, incompressible flow Navier-Stokes equation (RANS) combined with Shear Stress Turbulence (SST) model were used in this works to solve flow problem over the paper planes. The analysis is mainly conducted to study and compare the lift coefficient (), drag coefficient ()and aerodynamic efficiency () performances for each paper planes. The results show that the Glider paper plane has managed to produce better performances in terms overall magnitude, stall angle, wider angle of attack (?) envelope and higher maximum lift coefficient magnitude compared to the other paper plane design. However, Glider paper plane has the least distributions by producing at least 14.3% larger magnitude compared to the other plane design at certain ? region. Instead, The Wide Stunt has promisingly produced better distribution by producing lower value compared to the other plane design. Based on performance, the Wide Stunt paper plane has produced better and maximum aerodynamic efficiency () magnitudes compared to the other design. Wide Stunt paper plane induced at least 6.4% better magnitude compared to the other paper plane design. Based on these results, it can be concluded that Wide Stunt paper plane has promising advantages which are very crucial for the paper plane especially during hovering operation, take-off and landing manoeuvre.

Hydrogen Stark Broadening by Model Electronic Microfields

1977 ◽  
Vol 32 (11) ◽  
pp. 1195-1206 ◽  
Author(s):  
Joachim Seidel
Keyword(s):  
Numerical Results ◽  
Unified Theory ◽  
Statistical Features ◽  
Line Profiles ◽  
Stark Broadening ◽  
Wide Range ◽  
Hydrogen Lines ◽  
Good Agreement

Abstract The Method of Model Microfields proposed by Brissaud and Frisch is applied to calculate Stark broadened profiles of hydrogen lines in the static ion approximation. Numerical results for L-α, H-α, and H-β are found to be in good agreement with those derived from the unified theory by Vidal, Cooper, and Smith over a wide range of plasma densities and temperatures. This demon­ strates that reliable line profiles may be obtained from the microfield distribution and covariance alone, more complicated statistical features being less important in this context.

scholarly journals Hydrodynamic Performance of Rectangular Heaving Buoys for an Integrated Floating Breakwater

2019 ◽  
Vol 7 (8) ◽  
pp. 239 ◽  
Author(s):  
Xiaoxia Zhang ◽  
Qiang Zeng ◽  
Zhen Liu
Keyword(s):  
Wave Energy ◽  
Numerical Results ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Wave Energy Converters ◽  
Floating Breakwater ◽  
Reaction Forces ◽  
Wave Conditions

Recently, the integrated development of wave energy converters and breakwaters has become popular, moving from traditional passive wave absorption to active energy capture. In this study, rectangular heaving buoys are considered as floating breakwater modules to absorb wave energy. A numerical wave tank is established based on Reynolds Averaged Navier-Stokes equation and User-Define-Function in ANSYS-Fluent commercial software. The numerical results show that incident wave conditions and submerged depth have significant effects on the heaving performance and wave energy absorption of a rectangular buoy. Flow structures around the buoy are shown to exhibit flow separations and vortex shedding, which can provide more information on buoy optimization. Power take-off (PTO) reaction forces are assumed to be a linear function of the translation velocities of the buoy. Numerical results demonstrate that a suitable PTO module can improve the wave power absorption by up to 34.2% for certain buoy and wave conditions, which is valuable for further investigations.

scholarly journals Development of a new empirical formula for prediction of triple point path

Shock Waves ◽  
2020 ◽  
Vol 30 (6) ◽  
pp. 677-686 ◽  
Author(s):  
W. Xiao ◽  
M. Andrae ◽  
N. Gebbeken
Keyword(s):  
Triple Point ◽  
Empirical Formula ◽  
Numerical Results ◽  
Two Dimensional ◽  
Fluid Density ◽  
Arbitrary Lagrangian Eulerian ◽  
Eulerian Formulation ◽  
Wide Range ◽  
Nodal Coordinates ◽  
Good Agreement

Abstract This paper develops a new empirical formula for the prediction of the triple point path in irregular shock reflection cases. Numerical simulations using a two-dimensional axisymmetric multi-material arbitrary Lagrangian–Eulerian formulation are employed to obtain the data of fluid density. Using the data of fluid density and nodal coordinates, the gradients of fluid density are determined and then used to generate numerical schlieren images. Based on these images, the triple point paths are derived and compared with the models of the Unified Facilities Criteria (UFC) and Natural Resources Defense Council (NRDC) as well as two models from the open literature. It is found that the numerically derived triple point paths are in good agreement with those predicted by a recently published model in the open literature for the typical ground range of shock wave propagation of up to 6 m. Considering the whole distance range, it is found that the agreement of different models of the triple point path with the numerical ones depends on the considered blast scenario, i.e., the scaled charge height. For small-scaled charge heights, the model of the UFC and the recently published model in the open literature are in better agreement with the numerical results than the other two models, whereas the NRDC model has the best agreement with the numerical results for large-scaled charge heights. Based on the numerical results, a new empirical formula is proposed for the prediction of the triple point path, which is valid for a wide range of the scaled charge heights from 0.5 to 3.5 m/kg1/3 and scaled ground distances up to 15 m/kg1/3.

scholarly journals Permeability Properties of Jointed Rock with Periodic Partially Filled Fractures

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Fei Ye ◽  
Jun-Chao Duan ◽  
Wen-Xi Fu ◽  
Xing-Yu Yuan
Keyword(s):  
Rock Mass ◽  
Analytic Solution ◽  
Jointed Rock ◽  
Navier Stokes ◽  
Rock Fractures ◽  
Rock Matrix ◽  
Clear Fluid ◽  
Navier Stokes Equation ◽  
Seepage Characteristics ◽  
Good Agreement

Rock fractures always influence the hydrological properties of a rock mass. To investigate the seepage characteristics of a rock mass with partly filled fractures, a mathematical model is established. In this model, the clear fluid in fractures is governed by the Navier-Stokes equation, and the fluid both in the porous medium and rock matrix are subjected to the Brinkman-Extended Darcy equation. The analytic solution of an equivalent permeability coefficient for a rock mass with partly filled fractures is solved, and it could be reduced to some special known results. Comparisons with experimental data show good agreement, thus verifying the validity of the present computations.

Numerical Study on Influence of Grid Density to Aerodynamic Characteristics of Typical Transport Configurations

2012 ◽  
Vol 220-223 ◽  
pp. 2437-2444
Author(s):  
Yun Tao Wang ◽  
Guang Xue Wang ◽  
De Hong Meng ◽  
Song Li
Keyword(s):  
Test Data ◽  
Numerical Study ◽  
Aerodynamic Characteristics ◽  
Numerical Results ◽  
Navier Stokes ◽  
Grid Refinement ◽  
Navier Stokes Equation ◽  
High Lift ◽  
Pressure Drag ◽  
Structured Mesh

Numerical simulations for the flows of typical transport configurations are performed by solving Navier-Stokes equation using TRIsonic Platform (TRIP). The purpose is to validate TRIP3.0 for the simulation of transport configurations. The configurations contain DLR-F6 and trapezoidal high lift configurations. For DLR-F6, the structured mesh and test data are obtained from DPW-III. The reference numerical results are obtained by CFL3D. For the high lift configurations, the structured mesh are generated with ICEM, and test data are obtained from HiLiftPW-1. For these configurations, the effects of grid density to aerodynamic characteristics are systematically studied. The numerical results are verified by comparison with experimental data and numerical results of CFL3D. Grid refinement leads to converged numerical results. It is demonstrated that grid density has little influence on friction drag, whereas significant influence on pressure drag for the DLR-F6 configurations. It has little influence on lift and momentum for the trapezoidal high lift configurations before stall, but has obvious influence near stall.

Numerical Modeling of Aerated Cavitation Using a Penalization Approach for Air Bubble Modeling Coupled to Homogeneous Equilibrium Model

2014 ◽  
Author(s):  
Petar Tomov ◽  
Sofiane Khelladi ◽  
Christophe Sarraf ◽  
Farid Bakir
Keyword(s):  
Fluid Flow ◽  
Mixture Model ◽  
Stokes Equations ◽  
Saturation Pressure ◽  
Homogeneous Mixture ◽  
Navier Stokes ◽  
Strain Rate Tensor ◽  
Computational Domain ◽  
Time Step ◽  
Homogeneous Mixture Model

Cavitation is a well-known physical phenomena occurring in various technical applications. It appears when the pressure of the liquid drops below the saturation pressure. Coupling aeration in a cavitating flow is a recent technique to control the overall effect of the cavitation. It is achieved by introducing air bubbles into the flow. In order to reveal and explore the behaviour of air gas in the vicinity of the cavitation region, the paper is oriented towards the physics of the colliding vapor phase bubbles and cavitating regions. The re-entrant jet may influence the dynamics of the bubbles as well as the frequency of cavitation separation. Therefore, a two-way coupling between the fluid flow and the introduced vapor is of capital importance. By penalizing the strain rate tensor in the Homogeneous Mixture Model, the two-way coupling has been achieved. The contact-handling algorithm is based on the projections of the velocity fields of the injected particles over the velocity field of the fluid flow. At each time step the gradient of the distance between the bubbles, is kept non-negative as a guarantee of the physical non overlapping. The bubbles’ collisions are considered as inelastic. The differential equations system is composed of the Navier-Stokes equations, implemented with the Homogeneous Mixture Model. A high-order Finite Volume (FV) solver based on Moving Least Squares (MLS) approximations is used. The code uses a SLAU-type Riemann solver for the accurate calculation of the low Mach numbers. The computational domain is a symmetrical 2D venturi duct with an 18°–8° convergent/divergent angles respectively.

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