Numerical Computations of MHD Flow on Hypersonic and Re-Entry Vehicles

2016 ◽  
Author(s):  
Filipe Dias ◽  
José Páscoa ◽  
Carlos Xisto
Keyword(s):  
Numerical Model ◽  
Mhd Flow ◽  
Magnetic Reynolds Number ◽  
Numerical Code ◽  
Test Case ◽  
Flow Equations ◽  
Good Comparison ◽  
Spatial Discretisation ◽  
Radio Blackout ◽  
Mission Operation

In hypersonic flight of reentry vehicles the radio blackout is a typical problem, in particular because it arises during a critical mission operation point. To mitigate this radio blackout the magnetic window concept is proposed. In this work a numerical model is presented to accurately simulate the effect of a magnetic field interacting with ionized plasma surrounding the vehicle. The numerical model is based on the MHD flow equations. Initially, the code is validated for pure hypersonic gas dynamics. Diverse high resolution spatial discretisation schemes, within a Finite Volume framework, are analyzed for robustness. Afterwards, the numerical code is further validated for MHD flows using the well-known Hartmann case. A very good comparison between numerical and analytical results is verified. This allows a proper validation of the method in terms of Lorentz force, in particular under low-magnetic Reynolds number conditions. A very tough test-case is finally computed, being typical of a reentry capsule geometry. The accuracy of the model is then verified for different applied magnetic fields.

Geometrical Parameters Influencing a Hybrid Mechanical Coupling

2012 ◽  
Vol 525-526 ◽  
pp. 161-164 ◽  
Author(s):  
Giuseppe Lamanna ◽  
Francesco Caputo ◽  
Alessandro Soprano
Keyword(s):  
Numerical Model ◽  
Carbon Fibre ◽  
Fibre Composite ◽  
Numerical Code ◽  
Zinc Alloy ◽  
Geometrical Parameters ◽  
Test Case ◽  
Carbon Fibre Composite ◽  
Mechanical Coupling ◽  
Carbon Fibre Reinforced Polymer

Coupling techniques for components of different materials is spreading in mechanical industry; the test case studied in this work deals with the connection of an aluminium alloy component with a carbon fibre composite one. In particular, the first component is made of an aluminium-zinc alloy and exhibits an isotropic behaviour, while the second is made of a carbon fibre reinforced polymer (CFRP) and shows a strongly anisotropic behaviour; both materials are widely used in engineering applications. A titanium bolt connects the parts. This work is focused on the influence of the geometrical parameters which characterize the coupling between the components. In particular, a study has been carried out on the influence of the shank-hole clearance, the bolt head size, the bolt preload and the shape of the bolt head. A numerical model has been built and statically tested; the results have been compared with the experimental ones from literature. Once validated, the same numerical model has been used to evaluate the performance of the joint in presence of a change of the above mentioned characteristic parameters. The required numerical analyses have been performed using Abaqus/Standard® numerical code.

Numerical Study on the Effect of a Submerged Breakwater Seaward of an Existing Breakwater for Climate Change Adaptation

2018 ◽  
Author(s):  
Athul Sasikumar ◽  
Arun Kamath ◽  
Onno Musch ◽  
Arne Erling Lothe ◽  
Hans Bihs
Keyword(s):  
Climate Change ◽  
Numerical Model ◽  
Transmission Coefficient ◽  
Numerical Study ◽  
Protective Measure ◽  
Test Case ◽  
Relative Width ◽  
Optimal Dimension ◽  
Submerged Breakwater ◽  
Design Storm

In coastal areas, climate change is causing mean sea level rise and more frequent storm surge events. This means the breakwaters are expected to withstand the action of more severe incident waves and larger overtopping rates than they were designed for. Therefore, these impacts may have a negative effect on the functionality such as overtopping above the acceptable limits, in addition to stability of these structures. A breakwater which has been partly damaged by a storm stronger than the design storm has weak spots that can easily be damaged further. One way of protecting these breakwaters subjected to climate change is to build a submerged breakwater on the seaward side. This study focuses on the use of numerical model for optimal dimension of a submerged breakwater to be used as a protective measure for an existing structure. Comparisons are made between transmission coefficient predicted in the numerical model and those calculated from different formulae in literature. The variation in transmission coefficient due to different relative submergence and relative width parameters for waves with different steepness is studied and curves showing the dependence of these parameters on wave transmission are made. These results are then used for a test case in Kiberg, Norway where a submerged breakwater is proposed in front of a existing damaged rubble mound breakwater. The optimal geometry generated on the basis of curves is then implemented in the local-scale finite element wave prediction model, CGWAVE.

scholarly journals NUMERICAL MODEL OF BREAKWATER WAVE FLOWS

1988 ◽  
Vol 1 (21) ◽  
pp. 149 ◽  
Author(s):  
Alex C. Thompson
Keyword(s):  
Mathematical Model ◽  
Numerical Model ◽  
Reflection Coefficient ◽  
Water Wave ◽  
Wave Equations ◽  
Seepage Flow ◽  
Experimental Results ◽  
Simplified Model ◽  
Flow Equations ◽  
Shallow Water Wave Equations

A mathematical model of flow on a sloping breakwater face is described and results of calculations compared with some experimental results to show how the model can be calibrated. Flow above the surface of the slope is represented by the shallow water wave equations solved by a finite difference method. Flow within the breakwater is calculated by one of two methods. A solution of the linear seepage flow equations, again using finite differences or a simplified model of inflow can be used. Experimental results for runup and reflection coefficient are from tests performed at HRL Wallingford.

An Efficient Numerical Model of Pulsating Combustion and Its Experimental Validation

2009 ◽  
Author(s):  
Luca Casarsa ◽  
Pietro Giannattasio ◽  
Diego Micheli
Keyword(s):  
Numerical Model ◽  
Combustion Chamber ◽  
Second Order ◽  
Operating Conditions ◽  
Gas Dynamics Equations ◽  
Time Step ◽  
Flow Equations ◽  
Tail Pipe ◽  
Flux Difference ◽  
Pulse Jet

A simple and efficient numerical model is presented for the simulation of pulse combustors. It is based on the numerical solution of the quasi-1D unsteady flow equations and on phenomenological sub-models of turbulence and combustion. The gas dynamics equations are solved by using the Flux Difference Splitting (FDS) technique, a finite-volume upwind numerical scheme, and ENO reconstructions to obtain second-order accurate non-oscillatory solutions. The numerical fluxes computed at the cell interfaces are used to transport also the reacting species, their formation energy and the turbulent kinetic energy. The combustion progress in each cell is evaluated explicitly at the end of each time step according to a second-order overall reaction kinetics. In this way, the computations of gas dynamic evolution and heat release are decoupled, which makes the model particularly simple and efficient. A comprehensive set of measurements has been performed on a small Helmholtz type pulse-jet in order to validate the model. Air and fuel consumptions, wall temperatures, pressure cycles in both combustion chamber and tail-pipe, and instantaneous thrust have been recorded in different operating conditions of the device. The comparison between numerical and experimental results turns out to be satisfactory in all the working conditions of the pulse-jet. In particular, accurate predictions are obtained of the device operating frequency and of shape, amplitude and phase of the pressure waves in both combustion chamber and tail-pipe.

Numerical Simulation of Thermo-Electro-Magnetic Performances in Supersonic Channel Flow

2006 ◽  
Author(s):  
Z. Xu ◽  
C. Lee ◽  
R. S. Amano
Keyword(s):  
Channel Flow ◽  
Gas Flow ◽  
Mhd Flow ◽  
Navier Stokes ◽  
Test Case ◽  
Splitting Algorithm ◽  
Square Duct ◽  
Mhd Generator ◽  
Electro Magnetic ◽  
Applied Fields

A compressible magnetohydrodynamic (MHD) model composed of MHD Navier-Stokes (N-S) equations and magnetic induction equations is proposed in the present study for analyzing the magnetohydrodynamic characteristics in MHD generator and MHD accelerator channels of Magneto-Plasma-Chemical propulsion system [10∼12]. A splitting algorithm based on an alternative iteration is also developed for solving the two sets of equations [9]. As a test case, a supersonic MHD flow in a square duct was simulated. The numerical results are compared with the results computed by solving the classical N-S equations for the perfect gas flow, together with the results computed utilizing the degenerate MHD N-S equations for the same channel flow with constant applied magnetic field. The thermo-electro-magnetic performances of the test cases with constant and variable applied fields are then discussed.

Range of Variability in the Dynamics of Semi-Cylindrical Friction Dampers for Turbine Blades

2008 ◽  
Author(s):  
Stefano Zucca ◽  
Daniele Botto ◽  
Muzio M. Gola
Keyword(s):  
Degrees Of Freedom ◽  
Turbine Blades ◽  
Numerical Test ◽  
Forced Response ◽  
Numerical Code ◽  
Test Case ◽  
Force Coefficient ◽  
System A ◽  
Flat Side ◽  
Fatigue Failures

Under-platform dampers are used to reduce resonant stresses in turbine blades to avoid high cycle fatigue failures. In this paper a model of semi-cylindrical under-platform damper (i.e. with one flat side and one curved side) for turbine blades is described. The damper kinematics is characterized by three degrees of freedom (DOFs): in-plane translations and rotation. Static normal loads acting on the damper sides are computed using the three static balance equations of the damper. Non-uniqueness of normal pre-loads acting on the damper sides is highlighted. Implementation of the model in a numerical code for the forced response calculation of turbine blades with under-platform dampers shows that non-uniqueness of normal pre-loads leads to non-uniqueness of the forced response of the system. A numerical test case is presented to show the capabilities of the model and to analyze the effect of the main system parameters (damper mass, excitation force, coefficient of friction and damper rotation) on the damper behavior and on the system dynamics.

Numerical and Experimental Investigation of a Semi-Technical Scale Burner Employing Model Synthetic Fuels

2009 ◽  
Author(s):  
Massimiliano Di Domenico ◽  
Peter Kutne ◽  
Clemens Naumann ◽  
Juergen Herzler ◽  
Rajesh Sadanandan ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Numerical Data ◽  
Diagnostic Techniques ◽  
Combustion Efficiency ◽  
Transport Equations ◽  
Numerical Code ◽  
Combustion Chambers ◽  
Flow Equations ◽  
Gas Turbine Combustion ◽  
Shift Reaction

In this paper the development and the application of a numerical code suited for the simulation of gas-turbine combustion chambers is presented. In order to obtain an accurate and flexible framework, a finite-rate chemistry model is implemented, and transport equations for all species and enthalpy are solved. An assumed PDF approach takes effects of temperature and species turbulent fluctuations on the chemistry source term into account. In order to increase code stability and to overcome numerical stiffness due to the large-varying chemical kinetics timescales, an implicit and fully-coupled treatment of the species transport equations is chosen. Low-Mach number flow equations and k-ε turbulence model complete the framework, and make the code able to describe the most important physical phenomena which take place in gas-turbine combustion chambers. In order to validate the numerical simulations, experimental measurements are carried out on a generic non-premixed swirl-flame combustor, fuelled with syngas-air mixtures and studied using optical diagnostic techniques. The combustor is operated at atmospheric and high-pressure conditions with simulated syngas mixtures consisting of H2, N2, CH4, CO. The combustor is housed in an optically-accessible combustion chamber to facilitate the application of chemiluminescence imaging of OH* and planar laser-induced fluorescence (PLIF) of the OH-radical. To investigate the velocity field, particle image velocimetry (PIV) is used. The OH* chemiluminescence imaging is used to visualise the shape of the flame zone and the region of heat release. The OH-PLIF is used to identify reaction zones and regions of burnt gas. The fuel composition is modelled after a hydrogen-rich synthesis gas, which can result after gasification of lignite followed by a CO shift reaction and a sequestration of CO2. Actual gas compositions and boundary conditions are chosen so that it is possible to outline differences and similarities among fuels, and at the same time conclusions about flame stability and combustion efficiency can be drawn. A comparison between experimental and numerical data is presented, and main strengths and deficiencies of the numerical modelling are discussed.

Entrance Development of the Weakly Interacted MHD Plane Channel Flow as Affected by Wall Conductances

1971 ◽  
Vol 38 (3) ◽  
pp. 665-673 ◽  
Author(s):  
Edward S. Hsia
Keyword(s):  
Plane Channel ◽  
Mhd Flow ◽  
Skin Friction Coefficient ◽  
Magnetic Reynolds Number ◽  
Local Pressure ◽  
Electrically Conducting ◽  
Wall Conductivity ◽  
Conductance Parameter ◽  
Momentum Integral ◽  
Plane Channel Flow

Growth behavior of the weakly interacted laminar MHD flow in the entrance region of a plane channel with electrically conducting walls is investigated by the momentum integral method. In the developing region, the analysis shows that, with moderate magnetic Reynolds number, the nonuniformity of the magnetic field is found to be significant, and the effect of wall conductivity is found to shorten the growth history of the flow field. Numerical results, including local pressure gradient and skin-friction coefficient, are obtained over a range of Hartmann numbers of 0–10, and wall conductance parameter γ, defined as σwh/σa, of 0–20.

On the 3-D inverse potential target pressure problem. Part 2. Numerical aspects and application to duct design

1995 ◽  
Vol 282 ◽  
pp. 147-162 ◽  
Author(s):  
V. Dedoussis ◽  
P. Chaviaropoulos ◽  
K. D. Papailiou
Keyword(s):  
Companion Paper ◽  
Staggered Grid ◽  
Finite Difference Schemes ◽  
Computational Techniques ◽  
Test Case ◽  
Flow Equations ◽  
Potential Target ◽  
Reproduction Test ◽  
Target Pressure ◽  
Stream Function Formulation

A potential function/stream function formulation is introduced for the solution of the fully 3-D inverse potential ‘target pressure’ problem. In the companion paper (Part 1) it is seen that the general 3-D inverse problem is ill-posed but accepts as a particular solution elementary streamtubes with orthogonal cross-section. Under this simplification, a novel set of flow equations was derived and discussed. The purpose of the present paper is to present the computational techniques used for the numerical integration of the flow and geometry equations proposed in Part 1. The governing flow equations are discretized with centred finite difference schemes on a staggered grid and solved in their linearized form using the preconditioned GMRES algorithm. The geometry equations which form a set of first-order o.d.e.s are integrated numerically using a second-order-accurate space marching scheme. The resulting computational algorithm is applied to a double turning duct and a 3-D converging-diverging nozzle ‘reproduction’ test case.

Development and Validation of Numerical Model for Predicting Electromagnetic Expansion of Composite Rings

2013 ◽  
Vol 198 ◽  
pp. 627-632
Author(s):  
Jacek Janiszewski ◽  
Robert Panowicz
Keyword(s):  
Numerical Model ◽  
Ring Expansion ◽  
Constitutive Relationship ◽  
Numerical Code ◽  
Expansion Process ◽  
Ring Specimen ◽  
Good Convergence ◽  
Composite Ring ◽  
High Strain Rate Deformation ◽  
Development And Validation

In the present work, the description of a numerical model for predicting the electromagnetic composite ring expansion process and validation of a developed numerical code is presented. The strength response of rings materials under high strain rate deformation was described by using the well-known JohnsonCook constitutive relationship. Numerical considerations and experimental validation were performed for a composite ring consisted of a copper drive ring and X37CrMoV51 steel ring specimen. The analyses of the obtained results allow to find out that good convergence of theoretical and experimental data was achieved.

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