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    cursor near the name of the line and click once A data input box appears with the current number of cells Change it by typing in the correct number and press RETURN To quit from this mode move cursor out of the black window and click once If the cursor is on a button the button is also picked Powers Used to modify the cell distribution on lines The powers can also be backwards pwr or symmetrical Spwr Operation similar to Cells Dimension Used to set grid dimension and default grid size You must do this before matching the grid Match Grid Once this option is selected you need to pick a frame for matching When a frame is picked you can see a panel of various parameters Make changes and select OK To unmatch a frame set corner index to 0 One option in the match panel is Grid check You can select it to switch on or off the grid orthogonality checking on the matched grid OK Write PIL commands in COPYQ1 and exit Normal Normalize the scale to fill the picture in the black window Reduce Reduce the scale of the picture You need to move cursor into the window and click at two positions The whole picture will be reduced to that size Magnify Enlarge the scale of the picture You need to move cursor into the window and click at two positions Picture within that area will be enlarged to fill the whole screen Z 0 000E 00 This button controls the third location of the current working plane It can be directly changed by activating this button and typing the new number High Value It shows the coordinate of the high boundary and controls the scale in the vertical direction Vertical Direction It shows and changes the vertical direction Low Value It shows the coordinate of the low boundary and controls the offset in the vertical direction Left Value It shows the coordinate of the left boundary and controls the offset in the horizontal direction Horizontal Direction It shows and changes the horizontal direction Right Value It shows the coordinate of the right boundary and controls the scale in the horizontal direction The VIEW sub system for Cartesian and polar grids The VIEW sub system provides a full screen menu driven graphic environment through which the user can view and MODIFY the grid When the command VIEW is issued a full screen graphic display will appear on the VDU with a menu panel on the right hand side of the screen providing the following options and information DIMENSION The number of cells in each coordinate direction is displayed under this heading in the form NX NY NZ GRID TYPE The current grid type is displayed under this heading To change the grid type position the cursor in the highlighted box labelled GT and click the mouse or press return enter 1 2 or 3 for the required grid type and press return PLANE AND

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/view.htm (2016-02-15)
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  • where LM is the mixing length LM0 is the unmodified mixing length Y UTAU Y ENUL YG is the normal distance from the wall UTAU is the friction velocity at the wall SQRT wall shear stress divided by density and ENUL is the laminar kinematic viscosity A 26 0 Y is the relevant Reynolds Number The formula implies that LM LM0 equals Y A in the immediate vicinity of the wall where Y is small Moreover since LM0 equals KAPPA Y there where KAPPA is the von Karman constant approximately 0 4 the implication is that LM equals 0 4 26 Y 2 near the wall and 0 4 Y far from it Other authors see for example Cebeci and Smith 1974 have proposed that the constant 26 0 should be replaced by a function of dimensionless quantities involving pressure gradients mass transfer the compressibility and other factors Van Driest s modification has been provided in PHOENICS as an extension to the y direction mixing length prescriptions in subroutine GXLEN which comprise EL1 GRND2 GRND7 GRND8 GRND9 see the HELP file entry provided for EL1 In view of the difficulty of prescribing the mixing length for arbitrary geometries the Van Driest extension has been restricted to those options which are the most commonly employed for two dimensional wall boundary flows and pipe and duct flows These EL1 options relate the mixing length to the y coordinate of the cell centres only and BFC formulations are not provided A description of these options is given under the help file entry EL1 The Van Driest modification is activated by setting IENUTA 5 in the Q1 file The wall boundary conditions must be set using GRND2 wall function PATCHes because the wall friction velocity UTAU is retrieved in subroutine GXLEN from patchwise storage

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/turmod/enc_t314.htm (2016-02-15)
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  • of article TURBULENCE MODELS IN PHOENICS 8 Wall functions Contents Introduction Equilibrium log law wall functions Non Equilibrium log law wall functions Roughness wall functions Printout of friction and heat

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/turmod/enc_tu8.htm (2016-02-15)
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  • WinPhoton.HTM
    WinPHOTON created in the year 2003 by A Ginevsky and V Artemov is a graphics display package having the full functionality of PHOTON and AUTOPLOT and more but providing it by way of Windows like mouse clicks and dialog boxes

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_docs/winpho/winpho.htm (2016-02-15)
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  • Multi-fluid Combustion Model
    reactedness and that the 2 outflowing stream 3 consists of 100 fluids altogether in to be computed proportions The flow is steady Three cases will be shown with mixing and reaction constants respectively 10 10 50 10 and 50 20 This PDF is not unlike the 2 spike EBU presumption With increased mixing constant the PDF is not unlike an unsymmetrical clipped Gaussian With increased reaction constant the PDF is even more unsymmetrical 6 2 With non uniform fuel air ratio the 2D population In most combustors the fuel and oxidant enter separately so it is best to postulate a two dimensional population with say fuel air ratio and reactedness as the PDAs ie population distinguishing attributes The necessary number of fluids may then become large however it is possible to determine the necessary number by grid refinement studies Four results will be shown for a well stirred reactor in which the two entering streams are a fully unreacted lean mixture gas and a fully reacted rich mixture gas The population grids will be 3 by 3 too coarse 5 by 5 still too coarse 7 by 7 fairly good 11 by 11 more than fine enough Inspection of the average reactedness reveals the solution quality The 3 by 3 grid Note the value of average R ie reactedness The 5 by 5 grid Average R is much smaller The 7 by 7 grid Average R is a little smaller The 11 by 11 grid Average R is almost the same 6 3 Concluding remarks about the stirred reactor results The 100 fluids employed in the 1D population studies were surely too many Yet it is interesting to observe that such a number can be easily handled The shapes of the PDFs for the pre mixed case vary with the

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_lecs/mfm/mfm6.htm (2016-02-15)
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  • X-Cell: a new algorithm for fluid-flow simulation in PHOENICS
    components proportional to phiW phiO and phiO phiN W N S and E being located at the centroids of the sub cells Computation of associated distances and transport properties corresponds in an obvious manner to the above choices c The pressure gradient terms DIAGRAM 1 The velocities uWW and uW both experience momentum sources equal to 0 25 pOW pO the normal to x cell area for uniform grid The velocities uNW uSW uN and uS all experience momentum sources of one half that value The latter velocities all experience further momentum sources from pressure differences which they share with nodes farther west or farther east v and w velocities are handled similarly Distance weighting is used for non uniform grids d The source terms Sources due to chemical reaction radiation gravity ohmic heating and electromagnetic effects are given values proportional to sub cell volumes Turbulence energy generation terms are computed in the same way as for CCM with appropriate distribution between sub cells Distributed resistance momentum sources are given values proportional to cell volumes Wall boundary conditions are computed as sources in obvious ways only the near wall sub cell being involved 2 3 The solution procedure All sub cell values are currently solved point by point This is a temporary measure to be replaced by SIVA like procedures in the next stage of development SIVA Simultaneous Variable Adjustment was the favoured Imperial College algorithm until displaced by SIMPLE It has many merits and is due for revival Pressure is solved whole field as in SIMPLE whereafter the convection velocities w n s e above are corrected to ensure continuity satisfaction These corrections are shared also between the sub cell velocities 3 The square cavity study 3 1 The cases considered The square cavity with moving lid problem has been solved for the Reynolds number of 400 Heat transfer between the moving lid and the bottom surface has been included Uniform grids have been employed with NX and NY equal to each other and in successive runs to 11 21 31 41 51 61 71 81 91 and 101 The number of sweeps used has been sufficient for convergence for all the grids except possibly that with NX 101 Several thousand sweeps were used for the larger grids because the provisional point by point treatment makes convergence slow 3 2 Results of computations A selection of the results displayed will first be shown by way of contour and vector plots Thereafter some numerical results will be presented which enable their accuracy to be compared with those provided by the standard PHOENICS algorithm which employs a sta 1 ggered Cartesian grid What will first be shown are the vectors deduced from then mass flux velocities followed by contours of longitudinal velocity for each of the sub cells The grid has NX NY 21 Mass velocity vectors and east sub cell longitudinal velocity contours West sub cell and north sub cell longitudinal velocity contours South sub cell and cell averaged longitudinal velocity contours Numerical results 1 The following table shows the values of the minimum velocity on the centre line in the lid movement direction for various values of NX Below the values from the X Cell solutions are those for standard PHOENICS NX 11 21 31 41 51 61 71 81 91 101 XCell 187 267 302 317 322 329 329 329 3 317 Stnd 149 210 259 285 301 312 317 It should be noted that the X Cell results for the larger grids may not be completely converged Numerical results 2 The following table shows the values of Nusselt Number for the top wall times 0 5 for various values of NX Below the values from the X Cell solutions are those for standard PHOENICS NX 11 21 31 41 51 61 71 81 91 101 XCell 2 28 2 48 2 63 2 61 2 55 2 53 2 64 2 34 Stnd 2 15 2 134 2 16 2 25 2 25 2 27 2 28 It should be noted that the X Cell results for the larger grids may not be completely converged for the scalar equation solution procedure at present is slower than that of the momentum equations 3 3 Comparisons with standard PHOENICS Inspection of the table containing minimum velocity data suggests that The X Cell results for NX NY 61 probably represent the most accurate ones for those with finer grids reveal irregularities suggestive of incomplete convergence Standard PHOENICS needs appreciably finer grids to achieve comparable accuracy However since X Cell for a given NX stores nearly four times as many dependent variables as does standard PHOENICS the accuracy improvement is no more than in proportion to the number of these variables Therefore although X Cell is always superior for a fixed number of pressure variables it may be that pressure plays such an important part in changing the direction of the flow in the cavity that it is the number of pressure cells which is critical in this case Inspection of the table containing heat transfer coefficient data suggests a rather greater superiority for X Cell in that it achieves the value of 2 28 with NX 11 whereas standard PHOENICS reaches that value only for NX 81 This is understandable for the thin boundary near the moving lid is decisive for heat transfer and the distance from the wall to the nearest sub cell is one third for X Cell of what it is for standard PHOENICS 4 The cylinder in cross flow 4 1 The cases considered One of the potential advantages of the X Cell algorithm is that it may permit curved boundary problems to be solved adequately with Cartesian or polar grids rather than body fitted ones Therefore one of the flow situations which has been chosen for simulation with the aid of X Cell is the steady flow over a circular sectioned cylinder Of the various cases investigated results for the following will be presented Flow past a cylinder at a Reynolds Number of 40 with a 36 13 Cartesian grid computed by the X Cell algorithm The same flow with a BFC grid having the same number of cells computed by the standard staggered grid algorithm The same flow computed by the X Cell algorithm with a coarser Cartesian grid of 27 13 cells The same flow computed by the X Cell algorithm with a finer Cartesian grid of 60 30 cells From comparison of 1 and 2 it is hoped to determine whether X Cell with a Cartesian grid can produce results of an accuracy comparable with those from standard PHOENICS with a staggered BFC grid From the successive grid refinements of cases 3 and 4 it is desired to establish how fine a grid is needed for grid independent solutions to be achieved 4 2 Results of computations First the 36 13 grids will be shown Then the velocity vectors longitudinal velocity contours and temperature contours will be presented Finally the recirculation length data will be reported for all three grid finenesses BFC and X Cell Cartesian grids employed 36 13 The following figures compare the solutions in respect of velocity and temperature fields BFC and X Cell grid velocity vectors NX NY 36 13 Longitudinal Cartesian velocity contours for the BFC and X Cell grids Temperature contours BFC and X Cell grids NX NY 36 13 The influence of grid fineness on the recirculation length has been found to be as follows NX NY X Cell BFC Measured 27 13 2 3 1 15 2 75 36 13 2 6 1 25 2 75 60 30 2 8 1 5 2 75 It is evident that the coarsest X Cell grid produces better results than those from the finest BFC grid 5 Discussion 5 1 Concerning the cases presented The work on the square cavity has shown that X Cell produces more accurate results than standard PHOENICS when both are using upwind differencing It is true that higher order schemes which are available in the Advanced Numerical Algorithms option of PHOENICS will improve the staggered grid solutions whereas such schemes have not yet been devised for X Cell Nevertheless the superiority of X Cell over standard PHOENICS is such that an X Cell solution is often more accurate than a standard PHOENICS solution with twice the number of cells in every direction and it also uses less computer storage The slowness of convergence of the X Cell algorithm at the present time has to be admitted but it is an eradicable and therefore temporary feature Many means are available for introducing greater implicitness into the solution procedure and now that the inherent accuracy and stability of X Cell has been established attention will immediately be given to introducing these means PHOENICS has in any case too long suffered the disadvantages of the sequential mode of solving for one variable after another For chemical reactions for multi phase flow for advanced turbulence models and for many other circumstances in which strong interactions exist between different variables associated with the same cell sequential solution is NOT the best X Cell may provide the stimulus which leads to an appropriate consideration of variable to variable links The results presented for the circular cylinder flows are probably even more significant for they suggest that curved boundary flows may be computed more accurately with coarse Cartesian X Cell grids than with BFC grids with greater numbers of cells Suggest is the right word for there are many more cases which should be tried before a firm conclusion can justifiably be drawn The exploration of a wider range of examples is a matter of great urgency Three examples of practical applications of X Cell will now follow Comparisons with experimental data or BFC solutions have not yet been made 1 X junction carved in block NB PHOTON does not understand the diagonal blockages Velocity vectors and temperature contours 2 The flow in a chamber with inserts of irregular shapes The flow over a cylinder and an airfoil 5 2 Concerning other already achieved results a Dimensionality Most of the examples shown in the present paper have concerned the XY plane however X Cell has been introduced into PHOENICS in a general manner and tests have shown that the implementation involving the Z direction is just as satisfactory Although X Cell is easiest to describe for two dimensional situations it is valid also for one and three dimensional ones The following picture shows an example of a three dimensional calculation the purpose of which is to illustrate the low dispersion characteristics of X Cell which it inherits from CLDA The grid is 5 x 5 x 5 This is an example of low dispersion behaviour of pyramidal Std PHOENICS solution sub cells Velocity components are fixed at U1 V1 W1 sqrt 3 3 Step scalar discontinuity X Cell CLDA solution along the diagonal plane 45 degree step change X Y Z b Conjugate heat transfer The X Cell algorithm handles without difficulty the transfer of heat from solid to fluid whether the boundaries are aligned with the main cell walls or with their diagonals c Solid stress analysis PHOENICS has for several years been able to compute the displacements and therefore strains and stresses within solids immersed in fluids simultaneously with the velocities pressures and temperatures which give rise to those displacements This capability is incorporated in the solid stress option of PHOENICS The option has been little used so far and one of the reasons is that its satisfactory working has been GUARANTEED only for Cartesian grids whereas potential users have argued that curved surfaces demand body fitted coordinates X Cell has already been extended to problems in which stresses are solved for in the immersed solids simultaneously with the velocities etc in the fluids themselves Because X Cell is able to represent curved boundaries in Cartesian grids rather successfully as has been shown above it may provide what the PHOENICS solid stress option needs to secure acceptance The next two examples are of the solid and stress calculations using X Cell grids both for fluid flow and solid in stress calculations Temperature contours displacement vectors and stress contours in the solids 5 3 Concerning prospects and needs for the future a Prospects On the basis of experience so far there are good prospects that X Cell may become the most widely used algorithm in PHOENICS for flows with immersed solids it will be combined with ASAP which easily locates curvaceous bodies within Cartesian grids the computation of the stresses within those solids will become commonplace X Cell will use SIVA like solution strategies X Cell will be used for error estimating and thereafter for adaptive fine grid embedding X Cell will be combined with multi blocking and unstructured meshing b The need for simplified program set up At present the user of X Cell is required to introduce commands into the Q1 file which allocate storage for the sub cell variables which activate special XCEL and DPXCEL patches etc Such features are appropriate to an algorithm which is under development but if X Cell is to be frequently used it must suffice for users to insert XCEL T in their Q1 files XCEL T may indeed become the default setting Then the additional storage must be automatically provided and boundary condition data which users have supplied as though they were employing a staggered grid must be automatically translated into boundary conditions for sub cell variables c The need for full physics At present X Cell has been applied only to laminar flows of which the viscosity and Prandtl Schmidt numbers have been uniform within the fluid Extension to non uniform fluid properties presents no difficulties but it remains to be done and as is always the way doing so will necessitate some re thinking of the methods of computing and using properties within PHOENICS Turbulent flow simulation will require the energy generation terms to be coded and wall function strategies for walls coinciding with cell diagonals will have to be devised Two phase multi phase and free surface features are still to be activated in X Cell and chemical reaction radiation and other processes require to be exemplified d The need for a cylindrical polar X Cell formulation So many items of engineering equipment are tubular in form that the CARTES F setting is frequently selected in the Q1 files of PHOENICS Even though X Cell can it appears handle curved boundaries rather satisfactorily it would be perverse therefore to refrain from adapting it to polar coordinate grids The question of whether the sub cell velocity variables should be those aligned with the grid or remain as the Cartesian components is an open one and provided that care is taken in formulating the algebraic equations the solutions should be the same in both cases One special argument favours the choice of the Cartesian components it would be a useful step on the road to X Cell BFC e The need to allow some body fitting Despite the prospect of being able to dispense with BFC grids in many circumstances in which they are currently used it is to be expected that the requirement for some body fitting will remain For example flow in a turn around duct or in a sinuous tube will be best simulated by means of a grid which follows the duct or tube shape There will therefore inevitably be some pressure to develop a BFC version of X Cell and no difficulties of principle appear to stand in the way Probably the method will use the Cartesian components as the velocity variables f The need for extensive validation Finally it must be recognised that PHOENICS users will have confidence in the X Cell algorithm only when the validity of the flow simulations which it produces has been extensively demonstrated What has been presented here even augmented by other work which has been done but nor reported falls far short of what is needed 6 Conclusions The comparisons between the X Cell and staggered grid predictions for the square cavity show that X Cell provides significantly greater accuracy for a given computational expense The comparisons between the X Cell and BFC calculations for the cylinder in cross flow have shown that the accuracy of the X Cell solutions is comparable with those made with BFC grids of comparable number of cells The speed of convergence is slower for X Cell than for standard PHOENICS but the reasons are known and can be removed The prospects for the future of X Cell are good but much validation work is still needed Acknowledgements The assistance of Mr Nikolay Pavitsky of CHAM MEI in the development of the Fortran coding embodying the X Cell algorithm is gratefully acknowledged This work has been funded by Concentration Heat and Momentum Ltd Further notes by dbs June 2010 Contents 7 1 Developments since 1996 7 2 Advantages provided by X Cell 7 3 Solution procedures for scalars 7 4 Solution procedures for velocities 7 5 Solution procedures for pressure 7 6 The way forward 7 1 Developments since 1996 The X Cell capability described above was not then attached to the delivery version of PHOENICS because the concurrent developments connected with the Virtual Reality user interface were judged to constitute as much novelty as users could then be expected to tolerate Although this suspension was then thought of as being temporary it has in fact lasted until the present day June 2010 Many other developments have since 1996 been been attached to PHOENICS including GCV deemed to be a superior version of handling body fitted co ordinate problems PARSOL which enables bodies with curved surfaces to be handled without use of body fitted co ordinates MIGAL which provides some acceleration of convergence at the expense of an increased computer memory requirement by the use of a multi grid solver attachment

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/x-cell.htm (2016-02-15)
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  • COSP: Constant Optimising Software Package
    Optimising Software Package Contents What COSP is How COSP works What the input files are required to run COSP How to run COSP An example of COSP application to the

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_lecs/21years/cosp/cosp.htm (2016-02-15)
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  • PHOTON Help

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