Validation of Methods for Calculating Hydrogen Combustion in a Supersonic Model Air Flow Using the Experimental Data of Beach — Evans — Schexnayder

2019 ◽  
pp. 36-45
Author(s):  
N.V. Kukshinov ◽  
S.N. Batura ◽  
M.S. Frantsuzov
Keyword(s):  
Chemical Kinetics ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Fuel Mixture ◽  
Navier Stokes ◽  
Detailed Chemical Kinetics ◽  
Navier Stokes Equations ◽  
Kinetic Mechanisms ◽  
Relative Errors ◽  
Detailed Chemical

This paper deals with numerical simulation of combustion of a hydrogen-air mixture in a supersonic flow. The simulation is based on solving the complete system of Navier-Stokes equations with closure using the turbulence model and detailed chemical kinetics. The mixing and combustion of a hydrogen-air fuel mixture is considered in the experimental formulation of Beach-Evans-Schexnayder. The effect of various kinetic mechanisms, turbulence models, TCI models, and boundary conditions on the solution is studied qualitatively and quantitatively. The relative errors of mass concentration of water for control sections are determined, and the methods’ boundaries are shown. Conclusions are drawn on the influence of turbulent mixing mechanisms and chemical kinetics on the combustion of hydrogen.

scholarly journals Transient Pressure-Driven Electroosmotic Flow through Elliptic Cross-Sectional Microchannels with Various Eccentricities

Computation ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 27
Author(s):  
Nattakarn Numpanviwat ◽  
Pearanat Chuchard
Keyword(s):  
Laplace Transform ◽  
Electroosmotic Flow ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Mathieu Functions ◽  
Navier Stokes Equations ◽  
Flow Rates ◽  
Elliptic Cross ◽  
Flow Through ◽  
Relative Errors

The semi-analytical solution for transient electroosmotic flow through elliptic cylindrical microchannels is derived from the Navier-Stokes equations using the Laplace transform. The electroosmotic force expressed by the linearized Poisson-Boltzmann equation is considered the external force in the Navier-Stokes equations. The velocity field solution is obtained in the form of the Mathieu and modified Mathieu functions and it is capable of describing the flow behavior in the system when the boundary condition is either constant or varied. The fluid velocity is calculated numerically using the inverse Laplace transform in order to describe the transient behavior. Moreover, the flow rates and the relative errors on the flow rates are presented to investigate the effect of eccentricity of the elliptic cross-section. The investigation shows that, when the area of the channel cross-sections is fixed, the relative errors are less than 1% if the eccentricity is not greater than 0.5. As a result, an elliptic channel with the eccentricity not greater than 0.5 can be assumed to be circular when the solution is written in the form of trigonometric functions in order to avoid the difficulty in computing the Mathieu and modified Mathieu functions.

Effect of the turbulence models on Rushton turbine generated flow in a stirred vessel

2011 ◽  
Vol 1 (4) ◽  
Author(s):  
Wajdi Chtourou ◽  
Meriem Ammar ◽  
Zied Driss ◽  
Mohamed Abid
Keyword(s):  
Dissipation Rate ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Stirred Vessel ◽  
Rushton Turbine ◽  
Numerical Predictions ◽  
Volume Method

AbstractIn this paper, we performed a comparison of four turbulence models using for numerical simulation of the hydrodynamic structure generated by a Rushton turbine in a cylindrical tank. The finite volume method was employed to solve the Navier-Stokes equations governing the transport of momentum. In this study four closure models tested were: k-ɛ standard, k-ɛ RNG, k-ɛ Realizable and RSM (Reynolds Stress Model). MRF (Multi Reference Frame) technique was used with FLUENT software package. The present work aimed to provide improved predictions of turbulent flow in a stirred vessel and in particular to assess the ability to predict the dissipation rate of turbulent kinetic energy (e) that constitutes a most stringent test of prediction capability due to the small scales at which dissipation takes place. The amplitude of local and overall dissipation rate is shown to be strongly dependent on the choice of turbulence model. The numerical predictions were compared with literature results for comparable configurations and with experimental data obtained using Particle Image Velocimetry (PIV). A very good agreement was found with regards to turbulence.

scholarly journals Viscous Flow Calculations in Turbomachinery Channels

1989 ◽  
Author(s):  
Francesco Martelli ◽  
Vittorio Michelassi
Keyword(s):  
Stokes Equations ◽  
Turbulent Viscosity ◽  
Axisymmetric Flow ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Algebraic Expression ◽  
Two Dimensional ◽  
Approximate Factorization ◽  
Navier Stokes Equations ◽  
Flow Configurations

An implicit procedure based on the artificial compressibility formulation is presented for the numerical solution of the two-dimensional incompressible steady Navier-Stokes equations in the presence of large separated regions. Turbulence effects are accounted for by the Chien low Reynolds number form of the K-ε turbulence model and the Baldwin-Lomax algebraic expression for turbulent viscosity. The governing equations are written in conservative form and implicitly solved in fully coupled form using the approximate factorization technique. Preliminary tests were carried out in a laminar flow regime to check the accuracy and stability of the method in two-dimensional and cylindrical axisymmetric flow configurations. After testing in laminar and turbulent flow regimes and comparing the two turbulence models, the code was successfully applied to an actual gas turbine diffuser at low Mach numbers.

scholarly journals Enhanced Physics-Based Numerical Schemes for Two Classes of Turbulence Models

2009 ◽  
Vol 2009 ◽  
pp. 1-13
Author(s):  
Leo G. Rebholz
Keyword(s):  
Finite Element ◽  
Differential Operator ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Numerical Schemes ◽  
Discrete Laplacian ◽  
Navier Stokes Equations ◽  
Approximate Deconvolution ◽  
Finite Element Schemes

We present enhanced physics-based finite element schemes for two families of turbulence models, the models and the Stolz-Adams approximate deconvolution models. These schemes are delicate extensions of a method created for the Navier-Stokes equations in Rebholz (2007), that achieve high physical fidelity by admitting balances of both energy and helicity that match the true physics. The schemes' development requires carefully chosen discrete curl, discrete Laplacian, and discrete filtering operators, in order to permit the necessary differential operator commutations.

Multigrid Computation of Incompressible Flows Using Two-Equation Turbulence Models: Part II—Applications

1997 ◽  
Vol 119 (4) ◽  
pp. 900-905 ◽  
Author(s):  
X. Zheng ◽  
C. Liao ◽  
C. Liu ◽  
C. H. Sung ◽  
T. T. Huang
Keyword(s):  
Turbulent Flows ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Time Stepping ◽  
Grid Algorithm ◽  
High Reynolds

In this paper, computational results are presented for three-dimensional high-Reynolds number turbulent flows over a simplified submarine model. The simulation is based on the solution of Reynolds-Averaged Navier-Stokes equations and two-equation turbulence models by using a preconditioned time-stepping approach. A multiblock method, in which the block loop is placed in the inner cycle of a multi-grid algorithm, is used to obtain versatility and efficiency. It was found that the calculated body drag, lift, side force coefficients and moments at various angles of attack or angles of drift are in excellent agreement with experimental data. Fast convergence has been achieved for all the cases with large angles of attack and with modest drift angles.

The Effects of Using Formaldehyde as an Additive on the Performance of an HCCI Engine Fueled With Natural Gas

2010 ◽  
Author(s):  
Omid Jahanian ◽  
Seyed Ali Jazayeri
Keyword(s):  
Natural Gas ◽  
Chemical Kinetics ◽  
Thermodynamic Model ◽  
Fuel Mixture ◽  
Volumetric Efficiency ◽  
Detailed Chemical Kinetics ◽  
Operating Condition ◽  
Hcci Engine ◽  
Additive Content ◽  
Detailed Chemical

In this paper, the performance of a natural gas HCCI engine is studied through a thermodynamic model including detailed chemical kinetics. Then the influence of using formaldehyde as an additive on the engine characteristics has been investigated. Results show that it is possible to change engine working limits using this additive. Furthermore, there is an optimum additive content for each operating condition which leads to higher output work and power. It is also shown that the air/fuel mixture will ignite earlier using this additive so it is conceivable to reduce inlet mixture temperature resulting in better performance due to higher volumetric efficiency.

Computational Analysis of a Inverted Double-Element Airfoil in Ground Effect

2006 ◽  
Vol 128 (6) ◽  
pp. 1172-1180 ◽  
Author(s):  
Stephen Mahon ◽  
Xin Zhang
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Near Field ◽  
Turbulence Models ◽  
Ground Effect ◽  
Wake Flow ◽  
Navier Stokes ◽  
Main Element ◽  
Ride Height ◽  
Navier Stokes Equations

The flow around an inverted double-element airfoil in ground effect was studied numerically, by solving the Reynolds averaged Navier-Stokes equations. The predictive capabilities of six turbulence models with regards to the surface pressures, wake flow field, and sectional forces were quantified. The realizable k−ε model was found to offer improved predictions of the surface pressures and wake flow field. A number of ride heights were investigated, covering various force regions. The surface pressures, sectional forces, and wake flow field were all modeled accurately and offered improvements over previous numerical investigations. The sectional forces indicated that the main element generated the majority of the downforce, whereas the flap generated the majority of the drag. The near field and far field wake development was investigated and suggestions concerning reduction of the wake thickness were offered. The main element wake was found to greatly contribute to the overall wake thickness with the contribution increasing as the ride height decreased.

Strongly Coupled Fluid-Structure Interactions via a New Navier-Stokes Method for Prediction of Vortex-Induced Vibrations

2005 ◽  
Author(s):  
Yannis Kallinderis ◽  
Hyung Taek Ahn
Keyword(s):  
Stokes Equations ◽  
Computational Cost ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Design Tool ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Vortex Induced Vibrations ◽  
Offshore Industry

Numerical prediction of vortex-induced vibrations requires employment of the unsteady Navier-Stokes equations. Current Navier-Stokes solvers are quite expensive for three-dimensional flow-structure applications. Acceptance of Computational Fluid Dynamics as a design tool for the offshore industry requires improvements to current CFD methods in order to address the following important issues: (i) stability and computation cost of the numerical simulation process, (ii) restriction on the size of the allowable time-step due to the coupling of the flow and structure solution processes, (iii) excessive number of computational elements for 3-D applications, and (iv) accuracy and computational cost of turbulence models used for high Reynolds number flow. The above four problems are addressed via a new numerical method which employs strong coupling between the flow and the structure solutions. Special coupling is also employed between the Reynolds-averaged Navier-Stokes equations and the Spalart-Allmaras turbulence model. An element-type independent spatial discretization scheme is also presented which can handle general hybrid meshes consisting of hexahedra, prisms, pyramids, and tetrahedral.

scholarly journals Validation of atmospheric boundary layer turbulence model by on-site measurements

2010 ◽  
Vol 14 (1) ◽  
pp. 199-207 ◽  
Author(s):  
Zarko Stevanovic ◽  
Nikola Mirkov ◽  
Zana Stevanovic ◽  
Andrijana Stojanovic
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Linear Models ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Boundary Layer Turbulence ◽  
Askervein Hill ◽  
Neutral Conditions

Modeling atmosperic boundary layer with standard linear models does not sufficiently reproduce wind conditions in complex terrain, especially on leeward sides of terrain slopes. More complex models, based on Reynolds averaged Navier-Stokes equations and two-equation k-? turbulence models for neutral conditions in atmospheric boundary layer, written in general curvilinear non-orthogonal co-ordinate system, have been evaluated. In order to quantify the differences and level of accuracy of different turbulence models, investigation has been performed using standard k-? model without additional production terms and k-? turbulence models with modified set of model coefficients. The sets of full conservation equations are numerically solved by computational fluid dynamics technique. Numerical calculations of turbulence models are compared to the reference experimental data of Askervein hill measurements.

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