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- THE STRUCTURE OF GROUND

Ground Stations The logical variable USEGRX activates when TRUE the use of GREX itself The logical variable USEGRD activates if TRUE the call to the Ground Station called GROUND This is supplied as an empty form where users can write their coding The character variable NAMGRD which allows the attachment and activation of Ground Stations with names other than GROUND or GREX The Ground Subroutine The GROUND subroutine is just an empty example of Ground Station It is provided for the user to insert coding which supplements or even replaces the built in features At this point it is important to stress that GROUND is not called directly by EARTH EARTH calls GREX from where ALL the active Ground Stations are called in order The Group Arrangement And Flow Control The Ground Station is arranged in groups reflecting the group structure of input file Q1 These groups are visited at specific times during the computational procedure Some of them are visited always others only when the user instructs PHOENICS to do so by way of settings in the Q1 file In GROUND some groups are for convenience further organized into sections WHICH group and section is to be visited is controlled in GROUND by two integer variables IGR the group number ISC the section number These are set within Earth and passed onto GROUND via a COMMON statement IGR and ISC are thereafter used in GROUND for flow control via GO TO statements such as GO TO 1 2 3 4 5 6 7 8 9 10 11 12 13 14 25 25 25 25 19 20 25 1 125 23 24 IGR 25 CONTINUE RETURN C C C GROUP 1 Run title and other preliminaries C 1 GO TO 1001 1002 ISC 1001 CONTINUE The Groups and their functions Group 1 Preliminaries Group 1 of GROUND is ALWAYS VISITED at the beginning of each run Section 1 is used for the initialization of local variables and in general for any operation that has to be performed only once at the beginning of the computation Note that the user can in this section change the identification message written to the VDU This is a wise strongly recommended practice which allows to distinguish private versions of Earth from the public task Section 2 is used on some machines for special overlay practices It is otherwise seldom used Groups 2 To 5 Grid Specification Group 2 time is visited only when TLAST has been set to GRNDn in the Q1 file The time step size DT can be set in this group Group 3 x direction grid is visited only in parabolic calculations PARAB T when AZXU GRNDn The x extent of the domain can then be modified in GROUND as the computation proceeds downstream by setting XRAT to the ratio of XULAST s between the previous and the current slab This is adequate for instance for the simulation of jets and boundary layers in parabolic mode GROUP 4 y direction grid

Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_lecs/ground/ground1.htm (2016-02-15)

Open archived version from archive - THE USE OF GROUND

as follows Two kinds of information are therefore needed in order to access these values The starting position of the segment within the F array The order in which the slab values are stored within the segment The Zero Location Index The location just before the segment is called the zero location index These zero location indexes are allocated by PHOENICS at the beginning of the computation Their values depend on the problem dimensionally the variables solved for and stored whether the problem is steady or transient whether it is parabolic or elliptic etc The integer function L0F el zero ef provides given a flow variable index the zero location index for the current slab of values For instance the zero location index for the values of W1 on the current slab is L0F W1 The slab values of W1 are therefore stored in the segment F L0F W1 1 to F L0F W1 NX NY The Segment Structure The slab values for each variable are written in each segment in the following order First the NY cells at IX 1 then the NY cells at IX 2 finally the NY cells at IX NX Therefore the cell IX IY of the current slab of W1 is stored as F L0F W1 IY NY IX 1 Coding For The Example The coding for the example in this lecture using direct access to the F array would be 196 CONTINUE C SECTION 6 FINISH OF IZ SLAB L0W1 L0F W1 L0C1 L0F C1 L0C2 L0F C2 or L0C2 L0F LBNAME MASS DO IX 1 NX DO IY 1 NY I IY NY IX 1 F L0C2 I F L0W1 I F L0C1 I END DO END DO RETURN Note that the zero locations are obtained outside the loop as they are invariant for the slab They must be obtained at each slab however as they change from slab to slab The L0F function should never be used within an array reference as this is very inefficient Note also that the double loop IX IY above is in fact equivalent to the following single one DO I 1 NX NY F L0C2 I F L0W1 I F L0C1 I END DO As long as the loop covers the whole slab this is more efficient than a double loop The Two Methods Advantages And Disadvantages Choosing one of the two methods is to a great extent a question of personal preference However these are some subjective advantages and disadvantages m1 The FN library is a compact way of coding which circumvents the use of do loops Furthermore the FN subroutines have built in checks that decrease the chances of an error However the number of FN functions available is although large limited and the user might not find there what they are looking for Computational efficiency is good m2 The direct access to the F array is a powerful flexible and efficient method However there is no safety net once the zero locations have been obtained and changing the value of the wrong position in the F array is a very difficult error to trace Users will probably find themselves moving from the first option to the last as they build up expertise Spare Working Space The integer indices GRSP1 to GRSP10 provide access to auxiliary slabwise working space which can be used in the calls to FN subroutines and in the F array method Before one of these indices can be used space must be allocated for it in the F array This is effected in PHOENICS by a call to the subroutine MAKE in Group 1 Section 1 Example C GROUP 1 RUN TITLE AND OTHER PRELIMINARIES C 1 GO TO 1001 1002 ISC 1001 CONTINUE CALL MAKE GRSP1 CALL MAKE GRSP7 Example of usage Average value at each cell of the flow variables C1 to C10 CALL MAKE GRSP2 This in Group 1 Section 1 C FN1 Y A Y A This in eg Group 19 CALL FN1 GRSP2 0 0 Initialise GRSP2 to 0 0 DO IVARIA C1 C10 C FN60 Y X Y Y X CALL FN60 GRSP2 IVARIA GRSP 2 will hold the sum of C s END DO C FN25 Y A Y A Y CALL FN25 GRSP2 1 0 10 0 Now average A similar device is frequently used in GREX where another suite of indices EASP1 to EASP20 are available The EASP set can also be used in GROUND but then GREX should be checked for conflicting use Setting Fluid Properties Fluid properties can be set in Group 9 of GROUND following the methods outlined above for flow variables The only difference is in fact the integer index used to refer to the property Two related quantities are used in GROUND in connection with properties These are The value of the property e g RHO1 which is either a constant RHO1 1 0 or a flag if the property is to be computed in GROUND e g RHO1 GRND The integer index for a property which is available for use even when the property is not STOREd in the Q1 file The integer index is stated for each property at the top of its Section in Groups 9 and 10 e g DEN1 for RHO1 Storing properties is required for their relaxation and plotting with PHOTON The SATELLITE STORE command e g STORE RHO1 or STORE DEN1 EARTH will only allow access to the F array via the correct integer indices A list of properties and indices can be found by looking at group 9 of the GROUND subroutine The properties the thing set in Q1 to gain access to GROUND are given on the left the indices used to set the properties into the F array are given on the right Example Of Setting A Property We want to compute the temperature of the fluid as a function of enthalpy given by T H1 Cp where Cp is a constant Note that this

Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_lecs/ground/ground2.htm (2016-02-15)

Open archived version from archive - PHOENICS European User Meeting 2006 - Presentation not available

PHOENICS European User Meeting 2006 Presentation not yet available Back

Original URL path: http://www.cham.co.uk/PUC/PUM_London/notavailable.htm (2016-02-15)

Open archived version from archive - vancouvr.htm

or contents It will be seen that WGAP has a uniform value in the region of between the top of the duct and the tops of the upper metal slabs between which the actual distance is 0 008 meters Further it has approximately twice this value near the convex corners and it becomes zero in the concave corners next back or contents Contours of auxiliary quantities used in the fluid flow calculation The flow field was calculated by means of the LVEL turbulence model which makes use of the wall distance WDIS field This like WGAP is also derived from the LTLS distribution The contours of WDIS are displayed in Fig 13 which exhibits the expected maximum of 0 004 between the parallel horizontal walls and a somewhat greater value near the cavity where the true distance from the wall depends on the direction in which it is measured next back or contents LVEL like IMMERSOL is a heuristic model by which is meant that it is incapable of rigorous justification but is nonetheless useful WDIS is calculated once for all at the start of the computation From it and from the developing velocity distribution the evolving distribution of ENUT the effective turbulent viscosity is derived The resulting contours of ENUT are shown in Fig 14 Since the laminar viscosity is of the order of 1 e 5 m 2 s it is evident that turbulence raises the effective value far from the walls by an order of magnitude next back or contents c How the stresses were calculated As will be shown below the equations governing the displacements are very similar to those governing the velocities The CFD code PHOENICS like many others can calculate velocities in fluids but this ability is not needed in the solid region so such codes are usually idle there However PHOENICS can be tricked into calculating what it thinks are velocities everywhere whereas what it actually calculates in the solid regions are displacements The details of the trickery now follow next back or contents 3 The mathematics of the method a Similarities between the equations for displacement and velocity The similarities already referred to are here described for only one cartesian direction x but they prevail for all three directions next back or contents The x direction displacement U obeys the equation del 2 U d dx D C1 Te C3 Fx C2 0 where Te local temperature measured above that of the un stressed solid in the zero displacement condition multiplied by the thermal expansion coefficient D d dx U d dy V d dz W which is called the dilatation Fx external force per unit volume in x direction V and W displacements in y and z directions C1 C2 and C3 are functions of Young s modulus and Poisson s ratio next back or contents When the viscosity is uniform and the Reynolds number is low so that convection effects are negligible the x direction velocity u obeys the equation del 2 u d dx p c1 fx c2 0 where p pressure fx external force per unit volume in x direction c1 c2 the reciprocal of the viscosity next back or contents Notes The two equations are now set one below the other so that they can be easily compared del 2 U d dx D C1 Te C3 Fx C2 0 del 2 u d dx p c1 fx c2 0 The equations can thus be seen to become identical if p c1 D C1 Te C3 which implies D p c1 Te C3 C1 and fx c2 Fx C2 next back or contents The expressions for C1 C2 and C3 are C1 1 1 2 PR C2 2 1 PR YM where PR Poisson s Ratio and YM Young s Modulus and C3 2 1 PR 1 2 PR next back or contents A solution procedure designed for computing velocities will therefore in fact compute the displacements if the convection terms are set to zero within the solid region and the linear relation between D ie d dx U and p is introduced by inclusion of a pressure and temperature dependent mass source term next back or contents b Deduction of the associated stresses and strains The strains ie extensions ex ey and ez are obtained from differentiation of the computed displacements Thus ex d dx U ey d dx V ez d dx W next back or contents Then the corresponding normal stresses sx sy sz and shear stresses tauxy tauyz tauzx are obtained from the strains by way of equations such as sx YM 1 PR 2 ex PR ey and tauxy YM 1 PR 2 0 5 1 PR gamxy where gamxy d dy U d dx V next back or contents c The SIMPLE algorithm for the computation of displacements PHOENICS employs a variant of the SIMPLE algorithm of Patankar Spalding 1972 for computing velocities from pressures under a mass conservation constraint Its essential features are All the velocity equations are solved first with the current values of p The consequent errors in the mass balance equations are computed These errors are used as sources in equations for corrections to p The corresponding corrections are applied and the process is repeated next back or contents All that it is necessary to do in order to solve for displacements simultaneously is in solid regions to treat the dilatation B as the mass source error and to ensure that p obeys the above linear relation to it Therefore a CFD code based on SIMPLE can be made to solve the displacement equations by eliminating the convection terms ie setting Re low and making D linearly dependent on p and temperature T The staggered grid used as the default in PHOENICS proves to be extremely convenient for solid displacement analysis for the velocities and displacements are stored at exactly the right places in relation to p next back or contents 4 Details of the auxiliary models

Original URL path: http://www.cham.co.uk/PUC/PUC_Moscow/CHAM_Spalding.htm (2016-02-15)

Open archived version from archive - COSP

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 Virtual

Original URL path: http://www.cham.co.uk/PUC/PUC_Moscow/CHAM2_Wu/Cosp.htm (2016-02-15)

Open archived version from archive

IZ 13 2 637872E 01 1 802613E 01 1 624847E 01 1 542255E 01 1 496257E 01 1 469385E 01 1 455676E 01 1 454225E 01 1 465610E 01 1 492226E 01 1 544320E 01 1 655177E 01 1 977205E 01 3 527359E 01 IZ 14 2 636334E 01 1 802307E 01 1 624666E 01 1 542080E 01 1 496060E 01 1 469153E 01 1 455399E 01 1 453893E 01 1 465207E 01 1 491734E 01 1 543709E 01 1 654386E 01 1 975830E 01 3 523384E 01 IZ 15 2 632414E 01 1 801184E 01 1 623962E 01 1 541467E 01 1 495487E 01 1 468569E 01 1 454783E 01 1 453221E 01 1 464444E 01 1 490836E 01 1 542612E 01 1 652948E 01 1 973149E 01 3 515106E 01 IZ 16 2 625193E 01 1 798916E 01 1 622510E 01 1 540279E 01 1 494429E 01 1 467584E 01 1 453809E 01 1 452199E 01 1 463317E 01 1 489537E 01 1 541021E 01 1 650815E 01 1 968899E 01 3 501210E 01 IZ 17 2 615796E 01 1 795308E 01 1 620129E 01 1 538420E 01 1 492892E 01 1 466258E 01 1 452598E 01 1 451035E 01 1 462120E 01 1 488216E 01 1 539442E 01 1 648694E 01 1 964455E 01 3 488905E 01 IZ 18 2 645447E 01 1 799486E 01 1 621423E 01 1 538703E 01 1 492819E 01 1 466046E 01 1 452337E 01 1 450783E 01 1 461989E 01 1 488287E 01 1 539949E 01 1 650583E 01 1 973046E 01 3 583945E 01 SHEAR STRESS AT OUTTER FACE IZ 7 2 862020E 01 1 729599E 01 1 502061E 01 1 399251E 01 1 351841E 01 1 336024E 01 1 338339E 01 1 351251E 01 1 376440E 01 1 425211E 01 1 516474E 01 1 697489E 01 2 157301E 01 4 529932E 01 IZ 8 2 973689E 01 1 837613E 01 1 594415E 01 1 478873E 01 1 418455E 01 1 389339E 01 1 380855E 01 1 388174E 01 1 412002E 01 1 458563E 01 1 542661E 01 1 706710E 01 2 123700E 01 4 163072E 01 IZ 9 3 020453E 01 1 874562E 01 1 627920E 01 1 509700E 01 1 445863E 01 1 412819E 01 1 400457E 01 1 404541E 01 1 425620E 01 1 469025E 01 1 548901E 01 1 707193E 01 2 118550E 01 4 129275E 01 IZ 10 3 041603E 01 1 888975E 01 1 640844E 01 1 521804E 01 1 456781E 01 1 422271E 01 1 408381E 01 1 411051E 01 1 430874E 01 1 472947E 01 1 551358E 01 1 708125E 01 2 119705E 01 4 130908E 01 IZ 11 3 051626E 01 1 895161E 01 1 646235E 01 1 526771E 01 1 461224E 01 1 426106E 01 1 411578E 01 1 413655E 01 1 432954E 01 1 474505E 01 1 552409E 01 1 708716E 01 2 120639E 01 4 134021E 01 IZ 12 3 056245E 01 1 897832E 01 1 648483E 01

Original URL path: http://www.cham.co.uk/PUC/PUC_Moscow/CHEMTECH/SHEARSTRESS_DATA.txt (2016-02-15)

Open archived version from archive- 2002 Moscow PHOENICS User Conference - Presentation missing

2002 Moscow PHOENICS User Conference Presentation Missing Back

Original URL path: http://www.cham.co.uk/PUC/PUC_Moscow/missing.htm (2016-02-15)

Open archived version from archive - descr

is known to represent tube flow turbulence rather well Other possible choices are none which specifies that the flow should be treated as laminar and kemodl which activates for Reynolds numbers above 2000 the widely used k epsilon model The next box wherein gravity is set false F indicates that the effect of gravity on free convection is not to taken into account This being the case the next three boxes dealing with Cartesian components of the gravitational acceleration are of no importance When the effect of gravity is to be accounted for i e when the gravity setting is true T then 9 81 m s 2 is the gravitational acceleration acting in x direction in cartesian co ordinates This was the case for the calculation leading to the shown above velocity vectors and temperature contours Other choices can be made by the user if the tube is not placed horizontally 2 6 Initial conditions This group does not appear in the list because only steady i e not time dependent flow is being discussed 2 7 Boundary conditions The boundary conditions button opens the screen shown by the following image where the values of fluid inlet velocity inlet and external temperatures outlet pressure external heat transfer coefficient and fouling resistance have been grouped Because it is sometimes convenient to set the inlet velocity by way of the Reynolds number the pull down menu of the top right hand box allows this as the following image shows Only when the second choice has been made will values entered in the inlet velocity box be acted upon 2 8 Output The PHOENICS solver always produces an alphanumeric RESULT file but this usually contains too large an amount of data to interest the majority of users Therefore the designers of SimScenes make provision for a limited amount of information to be printed to the much smaller file called INFOROUT It is this which is displayed on the screen by default at the end of a simulation run A typical example can be seen by clicking here The output related button when clicked reveals that it is possible for the user to control the amount of information printed in Inforout All except the first of the boxes invite yes or no answers i e T or F to the implied question do you want to print the groups of items indicated on the right The number in the first box indicates how many times in the course of the run the values are to be printed If it is left at its unity default they will be printed once only at the end of the run If 2 is supplied there will also be a print out halfway through the run if 3 at one third and two thirds of the way etcetera Although the SimScene TubeFlow contains no examples the output group is where in other SimScenes menu items may be provided which control graphical output displays and even the nature and amount of what is printed in RESULT 2 9 Computational grid Pressing the computational grid button elicits the following screen This reveals that understandably the default grid is polar The 36 intervals in the circumfererential direction are each of 5 degrees The radial direction grid has two regions an inner one with 20 intervals for the fluid space inside the tube and an outer one with two intervals for the metal wall The outer region is shaded grey in the image below The longitudinal grid has 1 region containing 50 uniform intervals 2 10 Numerical The settings which may be changed in the final menu numerical are shown below about which it perhaps sufices to say That the flow simulating calculations proceed by way of repeated trial and error successive substitutions of the values of velocity temperature etc which are called iterations Here 100 is set as the default Often fewer than the set number are performed because the errors have been sufficiently reduced before then This is allowed to occur only when the second menu item is changed from T to F Sometimes unwelcome oscillations of values occur during the course of the calculation These can be reduced by setting less than unity values to so called relaxation factors of which one is available for each variable Those for longitudinal velocity and for temperature are here made accessible to the users of the TubeFlow SimScene 3 How to save the settings made for the TUBEFLOW simulation Having made many changes of the default settings the user may wish to keep them in order to repeat this calculation later They will be saved into the file named favorite xml from the input folder of any specific SimScene At the beginning this file does not exist There is the button List of saved parameter sets in the toolbar which enables the user to save his settings Clicking on this button opens the screen that follows There are no parameter sets saved so far Clicking on the Add current set of parameters button will result in the screen with an empty box for a new parameter set e g set1 Then click on the Save button These actions will result in the following The user can save as many sets of settings as he wishes adding them in the aforesaid manner to the favorite xml file in the input folder When the user wishes to use a saved set of parameters instead of the set with the default settings in this window he will have only to select the set in question and then press the Use selected set button In the end do not forget to save all created sets clicking on the Save all sets button The other buttons in this window toolbar are as follows enables the name of any particular set to be changed replaces the currently selected set in the list with default set of settings deletes the selected set from the list stored in the

Original URL path: http://www.cham.co.uk/phoenics/d_sapps/tubeflow/docs/descr_en.htm (2016-02-15)

Open archived version from archive

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