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  • cfd cham PHOENICS simuserve info
    library of Fortran subroutines which the user may call from his application programmes to supply viscosities thermal conductivities diffusion coefficients and thermal diffusion ratios or coefficients calculated according to two approximations a fitting programme that generates polynomial fits to the detailed transport properties in order to make more efficient the calculations performed by the subroutine library The PHOENICS CHEMKIN Interface provides a range of facilities from which the user may choose those that he requires namely calculation of thermodynamic and transport properties of gas mixtures an improved formulation of the transport equations in the mixture averaged approximation including thermal diffusion the Soret effect calculation of source terms for laminar flow for chemical species and enthalpy that result from chemical reactions when the system is to be solved within the usual PHOENICS methodology a fully implicit solver for the solution of the chemical species and enthalpy variables in laminar flow reacting systems with stiff chemical source terms the calculation of inlet properties ie the inflowing enthalpy of the gas mixture and either the mass flux from the inlet gas velocity or an inlet gas speed from the inlet mass flux CHEMKIN is extensively used in connexion with the PHOENICS CVD special purpose program For more complete information about CHEMKIN and the PHOENICS interface to it click here CHEMKIN and the interface may be ordered from CHAM back to top GENIE GENIE is an interface program supplied as part of PHOENICS which facilitates the linking of PHOENICS including multi block with third party grid generators and viewers especially those devised originally for finite element packages GENIE consists of two parts a set of subroutines used for the conversion of grids and patches from external programs into SATELLITE Q1 and XYZ files called the PEN PHOENICS Element Neutral file system and a set

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_info/addons.htm (2016-02-15)
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  • and has a fineness which the user determines by specifying the number of grid intervals in each direction PHOENICS then examines the facets defining the objects and having determined on which side of the facet the cell centre lies fills the whole of the cell with solid or fluid The PHOENICS solver is additionally able to respond to user s specifications of regions in which grid refinement is thought to be necessary by means of what is called the FGEM fine grid embedding technique All that is necessary in order to use this is to define the size and location of the bounding box of the grid refinement region and define the refinement ratios to be employed in the three different directions The PHOENICS solver has also been equipped with the PARSOL feature which whenever an object defining facet intersects a computational cell obliquely calculates the intersections of the facets with the cell edges and then does what is necessary to ensure that the terms in the algebraic representations of the conservation equations are properly modified FGEM and PARSOL can be used in combination to such effect that it may be argued the case for using body fitted coordinates is much diminished How the CAD to CFD path can be quickly traversed by CAD literate engineers by the use of PHOENICS can be seen by clicking here The capabilities of the FGEM and PARSOL techniques can be best be displayed by a tour of the relevant parts of the PHOENICS Applications Album which can be entered by clicking here Legitimate conclusions from detailed inspection of the just mentioned material appear to be The CAD to CFD transition can indeed be swiftly made entirely without grid creation difficulties The PARSOL technique with or without FGEM appears to be capable of procuring solutions of the hydrodynamic equations of an accuracy comparable with or superior to what can be achieved by means of body fitted grids whether structured or unstructured Fine grid embedding permits the focussing of attention on regions of especial importance and such focussing is achieved by simple mouse clicking operations The examples which have been shown do not however include the presence of thin walls such as are of importance in combustion chamber simulations 3 PARSOL applied to a 3D combustor a The problem considered In order to illustrate how PHOENICS can be used for simulating flows within combustors having curved walls without use of body fitted coordinate grids an idealized combustor model has been created which exhibits all the main geometrical features namely enlarging near constant and then diminishing cross section axial entry of two coaxial streams admission of additional air through film cooling slots admission of secondary air through apertures in the wall The geometry has not in fact been created by means of a standard CAD package but rather by a stand alone Fortran program utility which can make simple shapes very fast However that is not relevant to the present demonstration of the ability of PHOENICS to handle objects defined by facets whatever their origin Click here to go direct to PARSOL results The geometry is shown in the following screen dumps from the VR editor Figure 2 which is a view of the interior of the chamber seen from the outlet end Figure 3 which is a similar view but with more of the intervening solid cut away Figure 4 in which still more sight obstructing material has been removed and Figure 5 which because the viewing eye has drawn nearer and slightly changed the line of sight reveals more clearly the circular fuel entry and surrounding air entry on the left the annular film cooling slot one part of the surrounding wall and the rectangular secondary air entry aperture which has been cut in it The flow is steady and turbulent with use of the so called LVEL model for simplicity heat transfer results from the fact that the various streams enter at different temperature but chemical reaction has not been activated The same problem has been simulated in three different ways namely with a mono block cartesian grid with additionally an embedded fine grid and with PARSOL activated b The grid generation problem On this topic it perhaps suffices to say that there is no grid generation problem for the user because PHOENICS receives information about the shapes of the combustor walls and the apertures in them from the Virtual Reality data input module sole screen dumps from which constituted Figures t to 5 and from this information it deduces which computational cells are blocked by solid and which are not PHOENICS also detects whether regions have been specified as requiring grid refinement and does what is necessary without user intervention When Parsol has been activated by the appropriate button click in the menu the appropriate changes in the conservation equations are made automatically within the PHOENICS solver c Results of the stage 1 mono block grid calculation The following Figures represent various aspects of the first stage solution by way of screen dumps from the PHOENICS Virtual Reality Viewer Noteworthy features are The physical plausibility of all results The ability of the viewer to display many different aspects of the flow in as much detail as can reasonably be required The somewhat disquieting step like appearance of the curved and sloping walls which are probably associated with inaccuracies in the solution In parenthesis it may remarked that these inaccuracies may not be as great as those arising when badly skewed body fitted grids are employed The appearance of the steps is probably worse than their effect stage 1 pressures which shows the above mentioned step effect It should be noted that chamber wall defining objects are shown only in wire frame view and several have been hidden so that the contour plots can be seen more clearly stage 1 temperatures from the same viewpoint stage 1 velocities likewise stage 1 wall distances likewise The values of distance to the wall are of

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_lecs/cmbstr3/cmbstr3.htm (2016-02-15)
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    a more complete version of b The surface to surface radiation model Preliminary notes on each Models a b c and d use the radiative conductivity concept whereas model e allows fully for angular effects Of these only d can also handle conjugate heat transfer i e heat conduction within large immersed solids and two phase flow i e additional suspended solids within the flowing medium Model a is restricted to Cartesian and cylindrical polar grids whereas models b c and d are applicable to BFC grids also The PHOENICS implementation of all models is restricted to gray radiation i e to that in which the influence of wave length can be neglected Models d and e can handle radiation between solids separated by non absorbing media whereas the others cannot Model e is in principle the more accurate model d is the more economical Structure of this Encyclopaedia article Because of its novelty and wide applicability model d IMMERSOL is presented first in section 3 Sections 4 5 and 6 are devoted to the older models a b and c Model d is the only one to combine universal applicability with economic practicability for complex geometries Model e is

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/enc_rad2.htm (2016-02-15)
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  • extensions to account for wave length and temperature dependences can also be afforded users of commercial computer codes would be wise to ask whether those codes offer affordable approximations or non affordable exactnesses combined with tacit neglects 4 5 The MFM turbulence model for turbomachines and combustors Back to top Contents of section 4 5 The fundamental ideas Why turbo machinery designers need MFM A two fluid model prediction for turbo machinery MFM for combustion processes The significance of the 2D population distribution An example smoke production in a 3D gas turbine type combustor Discussion of the MFM smoke calculation Concluding remarks about MFM and its future a The fundamental ideas There are currently three approaches to the quantitative prediction of turbulent flow phenomena namely use of Kolmogorov type models which solve equations for quantities such as energy and dissipation ie k and epsilon use of Monte Carlo methods seeking to compute probability density functions ie PDFs for important variables and use of multi fluid models ie MFMs which can be regarded computing DISCRETISED PDFs Spalding 1995 Approach 1 is almost universally followed but lacking the necessary physics it MIS guides designers of eg gas turbines Approach 2 of Dopazo O Brien type is followed by some combustor specialists but its expense deters all but the wealthiest Approach 3 of the same type has been little publicised but it is economical easy to use and contains the necessary physics b Why turbo machinery designers need MFM Back to top Axial flow compressors and turbines as used in aircraft propulsion and in ground or sea level power production are characterised by the rapid passing of one blade row behind another The slower moving boundary layer fluid from the upstream row becomes a wake of slower moving fluid fragments which are distributed across the entrance plane of the downstream row The turbulent mixture which passes from row to row through a turbo machine is therefore best represented as a population of fluids with say axial velocity as their distinguishing characteristic Approach 3 ie use of MFM is a practicable means of calculating the population distribution and its influence on the mean flow Research on the exploitation of this possibility is only now starting but its promise appears to be very great Further research on Kolmogorov type models is now hard to justify c A two fluid model prediction for turbo machinery Back to top The lowest member of the MFM family is the two fluid model Spalding 1987 with which some recent studies have been made There follow two pictures which show how the time mean velocity distribution of a blade row differs according to whether a two fluid or as is customary a single fluid model is presumed The differences are qualitatively similar but the small quantitative differences are what counts when blade row losses are to be computed If two fluid calculations can already provide meaningful guidance to turbo machinery designers much more can be expected from the full MFM

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_lecs/cad2sft/chap4.htm (2016-02-15)
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  • The parabolic option of PHOENICS

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_lecs/parab/parab.htm (2016-02-15)
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  • in the VR viewer The next picture shows the three successively finer grid regions from the side the grids from the side and the next picture shows the grids from behind the grids from behind Finally the pressure field which agrees well with such measurements as have been published for this vehicle Note The jagged appearance of the vehicle outline is a deficiency of the graphics package which was then

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_applic/movsol/wuacar/wuacar.htm (2016-02-15)
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  • Accuracy For CFD predictions to be realistic the use of fine grids is essential requiring powerful computers with large memory resources Speed For CFD techniques to be used routinely in design and production cycles fast computers are required to achieve reasonable iterative times Scalability As computing demands increase one can upgrade the parallel system by adding more processors thereby enhancing rather than repeating on the initial investment Economy Parallel computers give better price performance ratios than vector supercomputers 3 Features PHOENICS was the first general purpose CFD code to be ported generically to massively parallel computers Porting is based on domain decomposition where the computational domain is divided into sub domains The computational work related to each sub domain is then assigned to its own processor A modified version of the PHOENICS solver EARTH is replicated over all available processors and runs in parallel exchanging boundary data at appropriate times The PHOENICS pre and post processors SATELLITE and PHOTON run in sequential mode Rapid convergence of the solver is achieved due to the efficient sub domain coupling hence no additional sweeps are required The processors communicate using the standard message passing protocols i e PVM or MPI as used on all major parallel platforms therefore the code can run on any parallel machine that supports PVM or MPI Another ship simulation picture the grid 4 Benchmarking Demonstration platforms with 4 8 16 and 32 processors have been used to benchmark parallel PHOENICS The efficiency depends on the size and complexity of the case the more complex the better Even with simple cases with increasing grid size speed ups of 5 8 14 and 23 respectively are achieved compared wit the same cases run on high end serial workstations The simulation results matched those on serial runs and from the user

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_lecs/parall/par.htm (2016-02-15)
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    D taking into account all the major features of its design any number of anodes in any arrangement the frozen electrolyte freeze around the edge of the cell distortion of the metal electrolyte interface due to pressure differences and due to vertical Lorentz Forces erosion of the anode undersides to follow the shape of the metalelectrolyte interface and current generation due to the motion of the metal the induced current The program solves the fundamental governing equations for three components of metal velocity three components of electrolyte velocity the pressure the gas fraction under the anodes and the inter anode gaps and the electric potential distribution Based on these it deduces the height of the metal electrolyte interface and the height of the electrolyte free surface and the electric current distribution and the induced currents These together with given magnetic fields are used to compute the Lorentz forces which drive the flow ESTER Extensions ESTER is configured to be easily extendible either by the user or by CHAM Features which can easily be added if required for a particular application include thermal calculations including the formation of freeze calculation of aluminium oxide concentration in the electrolyte interface to magnetic field

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_phoen/ester.htm (2016-02-15)
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