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  • CONWIZ : The 'Convergence-Promoting Wizard' for PHOENICS
    turbine combustor A somewhat tougher test of the capabilities of CONWIZ is provide by this case also a veteran by reason of its more numerous active physical processes including turbulence and chemical reaction Once again the effects of the standard and CONWIZ settings are compared by way of the graphical monitor plots which may be displayed by clicking below standard and conwiz This time the slower convergence of CONWIZ is more noticeable However it is gratifying to observe that convergence has been achieved with CONWIZ T as the only setting which the user has had to make It should also be remarked that although the maximum absolute corrections appear to fluctuate more wildly for CONWIZ their actual values are extremely small next Library case w802 the nuclear steam generator CONWIZ has not yet been taught anything specific about two phase flow it is therefore interesting to see what happens when it is presented with another classic case This is the nuclear steam generator which was the application which long ago led to both to the invention of the IPSA algorithm and to the creation of PHOENICS itself CONWIZ is being asked to tackle this problem without even being given a hint by way if FIINIT STEAM about the expected volume fractions of steam and water in the generator The next two pictures show the relevant monitor plots standard and conwiz Not bad for a beginner one might conclude although the levelling off of some residuals requires examining Since the selection of relaxation parameters for two phase flow is notoriously difficult this first time success of CONWIZ is especially encouraging next Library case b524 the Mizuki impeller CONWIZ has been kept in equal ignorance of the specific features of body fitted coordinate calculations which it therefore treats in the same way as those with cartesian or polar coordinates The results for the veteran Mizuki impeller problem are shown in the next two graphical monitor plots standard and conwiz Convergence is good for both the standard and the CONWIZ settings but the episode at the end of the CONWIZ run raises the question why However this question is as much about the credibility of the residual plots as it is about the success of CONWIZ Also interesting is what happens when the rotation speed is increased tenfold This is shown by the next pair of plots stan 10 and conw 10 Evidently CONWIZ handles the change without difficulty but the standard settings no longer procure convergence next Library case i205 temperatures in a computer room Convergence is particularly difficult to procure for flows with natural convection for sometimes differing false time steps may be required for the vertical direction velocity the horizontal velocities the temperature If CONWIZ can handle them well users of FLAIR the HVAC version of PHOENICS will be much relieved The next two picture provide some encouraging evidence in respect of library case i205 standard and conwiz It appears that CONWIZ performs quite as well as the standard settings next back or contents 5 How does CONWIZ work The main features of CONWIZ are as follows It starts by making guesses about reference values of length velocity density and temperature From these it deduces and sets some initial values of variables including the DVELDPs i e the rates of change of velocity with pressure difference at every point It sets linear under relaxation factors for all variables including the DVELDPs It sets maximum values to the increments per sweep for some variables In some circumstances it can improve its settings in the course of the computation next back or contents 6 How reliable is CONWIZ Does CONWIZ always work No However as the above examples have shown it often does pretty well When CONWIZ has failed to procure complete convergence it has sometimes transpired that there is some special instability promoter in the way in which the problem has been set up Fires represented as fixed heat sources regardless of flow conditions have led to solutions which not even CONWIZ can persuade to settle down CONWIZ has been in existence only since February 2004 and has not been receiving full time attention too much should therefore not yet be claimed for it Nevertheless to set CONWIZ T is certainly a wise thing to do at the start of a new calculation next back or contents 7 How can users participate in the promotion of convergence Although CONWIZ is ready to tackle any problem on its own it will respect user s settings and accept their assistance If users prefer to use false time step relaxation for any variable other than velocity CONWIZ will print a message questioning their wisdom but it will not change the settings It will however insist on using linear relaxation for velocities Any user set linear relaxation factor will be used in preference to its own User set VARMINs and VARMAXs will also be respected even if being too narrowly defined they distort the final solution next Probably the best thing a user can do in order to help CONWIZ in cases of difficulty is to use the new maximum absolute correction limitation by placing in the Q1 file such lines as SPEDAT MAXINC TEM1 R 10 0 This limits the maximum correction of temperature at any point in a singe sweep to 10 degrees The user can also instruct CONWIZ to start from user specified reference values by way of the following commands SPEDAT RLXFAC REFVEL R user set value SPEDAT RLXFAC REFLEN R user set value SPEDAT RLXFAC REFTEMP R user set value SPEDAT RLXFAC REFRHO R user set value Further if he or she is bold enough to use them further spedats will set upper and lower limits and relaxation factors for the individual DVELDPs This is however not advised Leave it to the wizard is the better rule to follow next back or contents 8 How can CONWIZ be further developed There is much scope for CONWIZ to improve its performance

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_docs/tr006/chap2.htm (2016-02-15)
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  • TR006 - Chapter 3: Fluid-structure interactions
    force integrated over the surface of the body but only if STORE SHRX SHRY SHRZ appears in Q1 The total forces in the X Y and Z coordinate directions The moments of the total force about the X Y and Z axes The deduced point of application of the force Facetted objects are those which do not use cuboid geometry files By default the geometry files for BLOCKAGE and PLATE

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_docs/tr006/chap3.htm (2016-02-15)
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  • TR006 - Chapter 4: The graphical user interface
    to fill the screen Section 4 3 Object Management Object dialog replaced by Object Management Panel and tabbed Object Specification dialog The old Object button and other buttons on the Main control panel have been replaced by the new Object Management dialog The design and layout of the window based Object Management is more rational and logical than the old Fortran panels Any column can be sorted in ascending order and a right click will bring up a context dialog as shown in the figure below The order of objects in the Q1 can be changed by right clicking on the Reference column This brings up a context menu from which the objects can be re ordered The New object dialog has become a tabbed dialog with the various options grouped onto individual panes Group handling facility A Group handling facility has been made available within the Object Management dialog It is invoked automatically if more than one object is selected The dialog allows standard Windows multiple selection using shift and control keys While the Object Management dialog is open multiple selection may also be achieved by holding the control key down while selecting an object in the main graphics window All selected objects can be moved together have their colour and transparency set or be revealed or hidden The group can be duplicated or arrayed moved deleted saved and retrieved All object geometries types and attributes will also be preserved The multiple group facility can be effectively used to create the model of a telephone exchange tower case shown in the following figure where many fans and PCBs can be grouped and arrayed Multiple Groups can be saved and read from the Q1 Propagation of Attribute Changes Changes made to the attributes for a member of a group are optionally propagated through the remainder of the group Section 4 4 Link to Shapemaker Link to Shapemaker directly from Object Specification dialog as described in Chapter 8 Section 4 5 Enhanced list of object types and enhancements to existing types The following new types of object have been added to the existing list of object types Wind profile object sets a logarithmic or power law boundary layer inlet velocity profile Drag lift object drag and lift calculation 3D At Plate objects the surface roughness and wall function type can be selected independently for each plate object and for each side of an internal plate At Blockage objects the surface roughness and wall function type can be selected independently for each solid blockage object In addition a user specified heat transfer coefficient can be set to replace the default wall function based value At Inlet objects for which the velocity or volume flow specification results in a fixed extraction rate the extraction mass flow is calculated using the local in cell densities not the density calculated from the temperature and pressure set in the inlet dialog Assembly object master and related components structure A new object Assembly has been introduced The

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_docs/tr006/chap4.htm (2016-02-15)
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  • flairnew,htm
    insulation is measured in clo clothing unit tog European unit of thermal insulation or m 2 k w 1 clo 0 155 m 2 k w 1 tog 0 645 clo The practical range is between 0 clo no clothing and 4 clo Eskimo clothing 1lb 0 454kg corresponds roughly to 0 15 clo with 0 6 clo and 1 0 clo being typical of summer and winter clothing respectively The default value is 0 6 clo The Metabolic Rate is measured in met metabolic units or W m 2 1 met 58 15 W m 2 The appropriate value depends on the activity being undertaken see ISO 7730 and ISO 8996 0 8 met reclining 1 0 met seated relaxed 1 2 met sedentary activity office dwelling school laboratory 1 6 met standing light activity shopping laboratory light industry 2 0 met standing medium activity shop assistant domestic work machine work 1 9 met walking on the level at 2 km h 2 4 met walking on the level at 3 km h 2 8 met walking on the level at 4 km h 3 4 met walking on the level at 5 km h The default value is 1 2 met The external work is the part of the metabolic rate that is used up in the activity being performed rather than contributing to the heat balance of the individual concerned It is usually taken as zero and should always be less than the metabolic rate The default value is 0 0 The relative humidity individual comfort is influenced by the humidity of the air which affect the heat loss through the skin It is often sufficient to specify a reasonable value for a particular environment but it is also possible to calculate the humidity as part of the simulation The default value is 50 5 2 3 Predicted percentage dissatisfied PPD PPD is an index defined in ISO 7730 that predicts the percentage of a large group of people who are likely to feel too warm or too cool i e the percentage of a large group of people who would vote for values other than 0 1 or 1 on the thermal sensation scale used for PMV The required input parameters are the same as for PMV The following pictures show the PPD predictions at head height on upper level of a shopping mall The one with no vents shows that almost 100 of people would feel too warm whereas the one with vents shows this percentage much smaller 5 2 4 Draught Rating The draught rating is defined in ISO 7730 as the percentage of people dissatisfied due to draught using the following equation PPDR 34 T a V 0 05 0 62 0 37 V I 3 14 where T a is the local air temperature V is the local air velocity and I is the local turbulence intensity in In Flair it is derived from the local turbulence quantities and the local absolute

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_info/flair/flairnew.htm (2016-02-15)
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  • TR006 - Chapter 6. The PHOENICS Commander
    functions of each button appearing on the POLIS Top Page of the PHOENICS commander They are reprinted below The New User button will lead to a page designed for beginners and which will enable them to learn about PHOENICS to see it in action and to test drive it this button will also lead to a welcoming message containing suggestions for newcomers About PHOENICS opens up the full treasury of

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_docs/tr006/chap6.htm (2016-02-15)
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  • TR006 - Chapter 7. Shapemaker
    be activated directly from the Object Specification dialog as shown below The new Shapemaker can now add and store non geometric attributes of objects to files having the file extension POB for example Sunlight object as well as saving the shapes to files having the file extension DAT The formats of the POB and DAT files exported by Shapemaker are accepted by the VR Editor and Viewer The following figure

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_docs/tr006/chap7.htm (2016-02-15)
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  • TR006 - Chapter 8: "PHOENICS On-Line"
    release of PHOENICS 3 6 it will be made available for interactive use via the internet See http www in2itive biz cham Users simply require a username and password in order to gain access to unrestricted interactive use of the

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_docs/tr006/chap8.htm (2016-02-15)
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  • TR006 - Chapter 9: Dynamic storage
    and PINTO is handled dynamically The need to recompile and relink just to have larger arrays has finally been banished Initial memory allocations are read from the CHAM INI configuration file in the directory phoenics d allpro If memory is

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_docs/tr006/chap9.htm (2016-02-15)
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