chp26

Chapter 26. Alphanumeric Reporting

FLUENT provides tools for computing and reporting integral quantitiesat surfaces and boundaries. These tools enable you to nd the mass flowrate and heat transfer rate through boundaries, the forces and momentson boundaries, and the area, integral, flow rate, average, and mass aver-age (among other quantities) on a surface or in a volume. In addition,you can print histograms of geometric and solution data, set referencevalues for the calculation of nondimensional coecients, and computeprojected surface areas. You can also print or save a summary report ofthe models, boundary conditions, and solver settings in the current case.These features are described in the following sections.

Section 26.1: Reporting Conventions Section 26.2: Fluxes Through Boundaries Section 26.3: Forces on Boundaries Section 26.4: Projected Surface Area Calculations Section 26.5: Surface Integration Section 26.6: Volume Integration Section 26.7: Histogram Reports Section 26.8: Reference Values Section 26.9: Summary Reports of Case Settings

Reporting tools for the discrete phase are described in Section 19.13.

c Fluent Inc. November 28, 2001 26-1

Alphanumeric Reporting

26.1 Reporting Conventions

For 2D problems, FLUENT computes all integral quantities per unitdepth. For axisymmetric problems, all integral quantities are computedfor an angle of 2 radians.

26.2 Fluxes Through Boundaries

For selected boundary zones, you can compute the following quantities:

The mass flow rate through a boundary is computed by summingthe dot product of the density times the velocity vector and thearea projections over the faces of the zone.

The total heat transfer rate through a boundary is computed bysumming the total heat transfer rate, q = qc + qr, over the faces,where qc is the convective heat transfer rate and qr is the radiationheat transfer rate. The computation of the heat transfer throughthe face depends on the specied boundary condition. For example,the conduction heat transfer on a constant-temperature wall facewould be the product of the thermal conductivity with the dotproduct of the area projection and the temperature gradient. Forflow boundaries, the total heat transfer rate is the flow rate ofthe conserved quantity. Depending on the models that are beingused, the total heat transfer rate may include the convective flowof sensible or total enthalpy, diusive flux of energy, etc.

The radiation heat transfer rate through a boundary is computedby summing the radiation heat transfer rate qr over the faces. Thecomputation of the radiation heat transfer depends on the radiationmodel used.

For example, you might use flux reporting to compute the resulting massflow through a duct with pressure boundaries specied at the inlet andexit.

26-2 c Fluent Inc. November 28, 2001

26.2 Fluxes Through Boundaries

Flux Reporting with Particles and Volumetric Sources

Note that the reported mass and heat balances address only flow thatenters or leaves the domain through boundaries; they do not include thecontributions from user-dened volumetric sources or particle injections.For this reason, a mass or heat imbalance may be reported. To determineif a solution involving a discrete phase is converged, you can compare thisimbalance with the change in mass flow or heat content computed in theparticle tracking summary report. The net flow rate or heat transfer ratereported in the Flux Reports panel should be nearly equal to the Changein Mass Flow or Heat Content in the summary report generated fromthe Particle Tracks panel.

26.2.1 Generating a Flux Report

To obtain a report of mass flow rate, heat transfer rate, or radiationheat transfer rate on selected boundary zones, use the Flux Reports panel(Figure 26.2.1).

Report !Fluxes...The steps for generating the report are as follows:

1. Specify which flux computation you are interested in by selectingMass Flow Rate, Total Heat Transfer Rate, or Radiation Heat TransferRate under Options.

2. In the Boundaries list, choose the boundary zone(s) on which youwant to report fluxes.

If you want to select several boundary zones of the same type,you can select that type in the Boundary Types list instead. All ofthe boundaries of that type will be selected automatically in theBoundaries list (or deselected, if they are all selected already).

Another shortcut is to specify a Boundary Name Pattern and clickMatch to select boundary zones with names that match the spec-ied pattern. For example, if you specify wall*, all boundarieswhose names begin with wall (e.g., wall-1, wall-top) will be selected



Figure 26.2.1: The Flux Reports Panel

automatically. If they are all selected already, they will be dese-lected. If you specify wall?, all boundaries whose names consist ofwall followed by a single character will be selected (or deselected,if they are all selected already).

3. Click on the Compute button. The Results list will display theresults of the selected flux computation for each selected boundaryzone, and the box below the Results list will show the summationof the individual zone flux results.

Note that the fluxes are reported exactly as computed by the solver.Therefore, they are inherently more accurate than those computed withthe Flow Rate option in the Surface Integrals panel (described in Sec-tion 26.5).


26.3 Forces on Boundaries

26.3 Forces on Boundaries

You can compute and report the forces along a specied vector and themoments about a specied center for selected wall zones. This featurecan be used, for example, to report aerodynamic coecients such as lift,drag, and moment coecient for an airfoil calculation.

26.3.1 Computing Forces and Moments

The forces on a wall zone are computed by summing the dot productof the pressure and viscous forces on each face with the specied forcevector. In addition to the actual pressure, viscous, and total forces, theassociated force coecients are also computed, using the reference valuesspecied in the Reference Values panel (as described in Section 26.8). Theforce coecient is dened as force divided by 12v

2A, where , v, andA are the density, velocity, and area explicitly specied in the ReferenceValues panel. Finally, the summations of the pressure, viscous, and totalforces for all the selected wall zones are presented in both dimensionalform and as nondimensional coecients.

The moment vector about a specied center is computed by summing theproduct of the force vectors for each face with the moment vector|i.e.,summing the forces on each face about the moment center. In additionto the actual components of the pressure, viscous, and total moment, themoment coecients are also printed. The moment coecient is denedas the moment divided by the product of the reference dynamic pressure,reference area, and the reference length. Finally, the summations of thepressure, viscous, and total moments for all the selected wall zones arepresented in both dimensional form and as nondimensional coecients.

To reduce round-o error, a reference pressure (also specied in the Ref-erence Values panel) is used to normalize the cell pressure for computa-tion of the pressure force. For example, the net pressure force vector iscomputed as the vector sum of the individual force vectors for each face:

~Fp = nX

i=1

(p pref)An^ (26.3-1)

= nX

i=1

pAn^+ prefnX

i=1

An^ (26.3-2)



where n is the number of faces, A is the area of the face, and n^ is the unitnormal to the face. This normalization has implications when computingtotal force coecients for open domains. For closed domains, the addi-tional term introduced by the reference pressure cancels, but for opendomains the pressure normalization introduces a net force equivalent tothe product of the projected area of the missing portion of the domainand the specied reference pressure.

26.3.2 Generating a Force or Moment Report

To obtain a report for selected wall zones of forces along a speciedvector or moments about a specied center, use the Force Reports panel(Figure 26.3.1).

Report !Forces...

Figure 26.3.1: The Force Reports Panel

The steps for generating the report are as follows:

1. Specify which type of report you are interested in by selectingForces or Moments under Options.


26.4 Projected Surface Area Calculations

2. If you choose a force report, specify the X, Y, and Z componentsof the Force Vector along which the forces will be computed. If youchoose a moment report, specify the X, Y, and Z coordinates of theMoment Center about which the moments will be computed.

3. In the Wall Zones list, choose the wall zone(s) on which you wantto report the force or moment information.

A shortcut that may be useful if you have a large number of wallzones is to specify a Wall Name Pattern and click Match to selectwall zones with names that match the specied pattern. For exam-ple, if you specify out*, all walls whose names begin with out (e.g.,outer-wall-top, outside-wall) will be selected automatically. If theyare all selected already, they will be deselected. If you specify out?,all walls whose names consist of out followed by a single characterwill be selected (or deselected, if they are all selected already).

4. Click on the Print button. In the console (text) window, the pres-sure, viscous (if appropriate), and total forces or moments, and thepressure, viscous, and total force or moment coecients along thespecied force vector or about the specied moment center will beprinted for the selected wall zones. The summations of the coe-cients and the forces or moments for all selected wall zones will beprinted at the end of the report.

26.4 Projected Surface Area Calculations

You can use the Projected Surface Areas panel (Figure 26.4.1) to computean estimated area of the projection of selected surfaces along the x, y,or z axis (i.e., onto the yz, xz, or xy plane).

Report !Projected Areas...The procedure for calculating the projected area is as follows:

1. Select the Projection Direction (X, Y, or Z).

2. Choose the surface(s) for which the projected area is to be calcu-lated in the Surfaces list.



Figure 26.4.1: The Projected Surface Areas panel

3. Set the Min Feature Size to the length of the smallest feature in thegeometry that you want to resolve in the area calculation. (Youcan just use the default value to start with, if you are not sure ofthe size of the smallest geometrical feature.)

4. Click on Compute. The area will be displayed in the Area box andin the console window.

5. To improve the accuracy of the area calculation, reduce the MinFeature Size by half and recompute the area. Repeat this step untilthe computed Area stops changing (or you reach memory capacity).

This feature is available only for 3D domains.


26.5 Surface Integration


You can compute the area or mass flow rate, or the integral, area-weighted average, flow rate, mass-weighted average, sum, facet average,facet maximum, facet minimum, vertex average, vertex minimum, andvertex maximum for a selected eld variable on selected surfaces in thedomain. These surfaces are sets of data points created by FLUENT foreach of the zones in your model, or dened by you using the methodsdescribed in Chapter 24.

Since a surface can be arbitrarily positioned in the domain, the value ofa variable at each data point is obtained by linear interpolation of nodevalues. For some variables, these node values are computed explicitlyby the solver. For others, however, only cell-center values are computed,and the node values are obtained by averaging of the cell values. Thesesuccessive interpolations can lead to small errors in the surface integra-tion reports. (Chapter 27 provides information on which variables havecomputed node values.)

Example uses of several types of surface integral reports are given below:

Area: You can compute the area of a velocity inlet zone, and thenestimate the velocity from the mass flow rate:

v =_mA

(26.5-1)

Area-weighted average: You can nd the average value on a solidsurface, such as the average heat flux on a heated wall with aspecied temperature.

Mass average: You can nd the average value on a surface in theflow, such as average enthalpy at a velocity inlet.

Mass flow rate: You can compute the mass flow rate through avelocity inlet zone, and then estimate the velocity from the area,as described above.

Flow rate: To calculate the heat transfer rate through a surface,you can calculate the flow rate of enthalpy.



Integral: You can use integrals for more complex calculations,which may involve the use of the Custom Field Function Calcula-tor panel, described in Section 27.5, to calculate a function thatrequires integral computations (e.g., swirl number).

26.5.1 Computing Surface Integrals

Area

The area of a surface is computed by summing the areas of the facetsthat dene the surface. Facets on a surface are either triangular orquadrilateral in shape.

ZdA =

nXi=1

jAij (26.5-2)

Integral

An integral on a surface is computed by summing the product of thefacet area and the selected eld variable, such as density or pressure.Each facet is associated with a cell in the domain. If the facet is theresult of an isovalue cut through the cell, the eld variable assigned tothe facet is the associated cell value. If the facet is on a boundary surface,an interpolated face value is used for the integration instead of the cellvalue. This is done to improve the accuracy of the calculation, and toensure that the result matches the boundary conditions specied on theboundary and the fluxes reported on the boundary.

ZdA =

nXi=1

ijAij (26.5-3)

Area-Weighted Average

The area-weighted average of a quantity is computed by dividing thesummation of the product of the selected eld variable and facet area bythe total area of the surface:



1A

ZdA =

1A

nXi=1

ijAij (26.5-4)

Flow Rate

The flow rate of a quantity through a surface is computed by summingthe product of density and the selected eld variable with the dot productof the facet area vector and the facet velocity vector:

Z~v d ~A =

nXi=1

ii~vi ~Ai (26.5-5)

Mass Flow Rate

The mass flow rate through a surface is computed by summing the prod-uct of density with the dot product of the facet area vector and the facetvelocity vector:

Z~v d ~A =

nXi=1

i~vi ~Ai (26.5-6)

Mass-Weighted Average

The mass-weighted average of a quantity is computed by dividing thesummation of the product of the selected eld variable and the absolutevalue of the dot product of the facet area and momentum vectors by thesummation of the absolute value of the dot product of the facet area andmomentum vectors (surface mass flux):

R~v d ~AR

~v d ~A =

Pni=1 ii

~vi ~AiPni=1 i

~vi ~Ai (26.5-7)



Sum

The sum of a specied eld variable on a surface is computed by summingthe value of the selected variable at each facet:

nXi=1

i (26.5-8)

Facet Average

The facet average of a specied eld variable on a surface is computedby dividing the summation of the cell values of the selected variable ateach facet by the total number of facets:

Pni=1 in

(26.5-9)

Facet Minimum

The facet minimum of a specied eld variable on a surface is the mini-mum cell value of the selected variable on the surface.

Facet Maximum

The facet maximum of a specied eld variable on a surface is the max-imum cell value of the selected variable on the surface.

Vertex Average

The vertex average of a specied eld variable on a surface is computedby dividing the summation of the node values of the selected variable ateach node by the total number of nodes:

Pni=1 in

(26.5-10)



Vertex Minimum

The vertex minimum of a specied eld variable on a surface is theminimum node value of the selected variable on the surface.

Vertex Maximum

The vertex maximum of a specied eld variable on a surface is themaximum node value of the selected variable on the surface.

26.5.2 Generating a Surface Integral Report

To obtain a report for selected surfaces of the area or mass flow rateor the integral, flow rate, sum, facet maximum, facet minimum, vertexmaximum, vertex minimum, or mass-, area-, facet-, or vertex-averagedquantity of a specied eld variable, use the Surface Integrals panel (Fig-ure 26.5.1).

Report !Surface Integrals...The steps for generating the report are as follows:

1. Specify which type of report you are interested in by selectingArea, Integral, Area-Weighted Average, Flow Rate, Mass Flow Rate,Mass-Weighted Average, Sum, Facet Average, Facet Minimum, FacetMaximum, Vertex Average, Vertex Minimum, or Vertex Maximum inthe Report Type drop-down list.

2. If you are generating a report of area or mass flow rate, skip tothe next step. Otherwise, use the Field Variable drop-down lists toselect the eld variable to be used in the surface integrations. First,select the desired category in the upper drop-down list. You canthen select a related quantity from the lower list. (See Chapter 27for an explanation of the variables in the list.)

3. In the Surfaces list, choose the surface(s) on which to perform thesurface integration.

If you want to select several surfaces of the same type, you canselect that type in the Surface Types list instead. All of the surfaces



Figure 26.5.1: The Surface Integrals Panel

of that type will be selected automatically in the Surfaces list (ordeselected, if they are all selected already).

Another shortcut is to specify a Surface Name Pattern and clickMatch to select surfaces with names that match the specied pat-tern. For example, if you specify wall*, all surfaces whose namesbegin with wall (e.g., wall-1, wall-top) will be selected automati-cally. If they are all selected already, they will be deselected. Ifyou specify wall?, all surfaces whose names consist of wall followedby a single character will be selected (or deselected, if they are allselected already).

4. Click on the Compute button. Depending on the type of report youhave selected, the label for the result will change to Area, Integral,


26.6 Volume Integration

Area-Weighted Average, Flow Rate, Mass Flow Rate, Mass-WeightedAverage, Sum of Facet Values, Average of Facet Values, Minimum ofFacet Values, Maximum of Facet Values, Average of Surface VertexValues, Minimum of Vertex Values, or Maximum of Vertex Values, asappropriate.

Note the following items:

Mass averaging \weights" toward regions of higher velocity (i.e.,regions where more mass crosses the surface).

Flow rates reported using the Surface Integrals panel are not asaccurate as those reported with the Flux Reports panel (describedin Section 26.2).

The facet and vertex average options are recommended for zero-area surfaces.


The volume, sum, volume integral, volume-weighted average, mass in-tegral, and mass-weighted average can be obtained for a selected eldvariable in selected cell zones in the domain.

Example uses of the dierent types of volume integral reports are givenbelow:

Volume: You can compute the total volume of a fluid region. Sum: You can add up the discrete-phase mass or energy sources to

determine the net transfer from the discrete phase. You can alsosum user-dened sources of mass or energy.

Volume integral: For quantities that are stored per unit volume,you can use volume integrals to determine the net value (e.g., in-tegrate density to determine mass).

Volume-weighted average: You can obtain volume averages of masssources, energy sources, or discrete-phase exchange quantities.



Mass integral: You can determine the total mass of a particularspecies by integrating its mass fraction.

Mass-weighted average: You can nd the average value (such asaverage temperature) in a fluid zone.

26.6.1 Computing Volume Integrals

Volume

The volume of a surface is computed by summing the volumes of thecells that comprise the zone:

ZdV =

nXi=1

jVij (26.6-1)

Sum

The sum of a specied eld variable in a cell zone is computed by sum-ming the value of the selected variable at each cell in the selected zone:

nXi=1

i (26.6-2)

Volume Integral

A volume integral is computed by summing the product of the cell volumeand the selected eld variable:

ZdV =

nXi=1

ijVij (26.6-3)

Volume-Weighted Average

The volume-weighted average of a quantity is computed by dividing thesummation of the product of the selected eld variable and cell volumeby the total volume of the cell zone:



1V

ZdV =

1V

nXi=1

ijVij (26.6-4)

Mass-Weighted Integral

The mass-weighted integral is computed by summing the product ofdensity, cell volume, and the selected eld variable:

ZdV =

nXi=1

iijVij (26.6-5)

Mass-Weighted Average

The mass-weighted average of a quantity is computed by dividing thesummation of the product of density, cell volume, and the selected eldvariable by the summation of the product of density and cell volume:

RdVRdV

=Pn

i=1 iijVijPni=1 ijVij

(26.6-6)

26.6.2 Generating a Volume Integral Report

To obtain a report for selected cell zones of the volume or the sum, vol-ume integral, volume-weighted average, mass-weighted integral, or mass-weighted average quantity of a specied eld variable, use the VolumeIntegrals panel (Figure 26.6.1).

Report !Volume Integrals...The steps for generating the report are as follows:

1. Specify which type of report you are interested in by selectingVolume, Sum, Volume Integral, Volume-Average, Mass Integral, orMass-Average under Options.

2. If you are generating a report of volume, skip to the next step.Otherwise, use the Field Variable drop-down lists to select the eld



Figure 26.6.1: The Volume Integrals Panel

variable to be used in the integral, sum, or averaged volume inte-grations. First, select the desired category in the upper drop-downlist. You can then select a related quantity from the lower list.(See Chapter 27 for an explanation of the variables in the list.)

3. In the Cell Zones list, choose the zones on which to compute thevolume, sum, volume integral, volume-weighted average, mass in-tegral, or mass-averaged quantity.

4. Click on the Compute button. Depending on the type of report youhave selected, the label for the result will change to Total Volume,Sum, Total Volume Integral, Volume-Weighted Average, Total Mass-Weighted Integral, or Mass-Weighted Average, as appropriate.


26.7 Histogram Reports

26.7 Histogram Reports

In FLUENT, you can print geometric and solution data in the console(text) window in histogram format or plot a histogram in the graphicswindow. Graphical display of histograms and the procedures for deninga histogram are discussed in Section 25.8.7.

The number of cells, the range of the selected variable or function, andthe percentage of the total number of cells in the interval will be reported,as in the example below:

0 cells below 1.195482 (0 %)2 cells between 1.195482 and 1.196048 (4.1666667 %)1 cells between 1.196048 and 1.196614 (2.0833333 %)0 cells between 1.196614 and 1.19718 (0 %)0 cells between 1.19718 and 1.197746 (0 %)2 cells between 1.197746 and 1.198312 (4.1666667 %)1 cells between 1.198312 and 1.198878 (2.0833333 %)6 cells between 1.198878 and 1.199444 (12.5 %)9 cells between 1.199444 and 1.20001 (18.75 %)25 cells between 1.20001 and 1.200576 (52.083333 %)2 cells between 1.200576 and 1.201142 (4.1666667 %)0 cells above 1.201142 (0 %)

To generate such a printed histogram, use the Solution Histogram panel.

Report !Histogram...Follow the instructions in Section 25.8.7 for generating histogram plots,but click on Print instead of Plot to create the report.



26.8 Reference Values

You can control the reference values that are used in the computationof derived physical quantities and nondimensional coecients. Thesereference values are used only for postprocessing.

Some examples of the use of reference values include the following:

Force coecients use the reference area, density, and velocity. Inaddition, the pressure force calculation uses the reference pressure.

Moment coecients use the reference length, area, density and ve-locity. In addition, the pressure force calculation uses the referencepressure.

Reynolds number uses the reference length, density, and viscosity. Pressure and total pressure coecients use the reference pressure,

density, and velocity.

Entropy uses the reference density, pressure, and temperature. Skin friction coecient uses the reference density and velocity. Heat transfer coecient uses the reference temperature. Turbomachinery eciency calculations use the ratio of specic

heats.

26.8.1 Setting Reference Values

To set the reference quantities used for computing normalized flow-eldvariables, use the Reference Values panel (Figure 26.8.1).

Report !Reference Values...You can input the reference values manually or compute them based onvalues of physical quantities at a selected boundary zone. The referencevalues to be set are Area, Density, Enthalpy, Length, Pressure, Temper-ature, Velocity, dynamic Viscosity, and Ratio Of Specic Heats. For 2Dproblems, an additional quantity, Depth, can also be dened. This value


26.8 Reference Values

Figure 26.8.1: The Reference Values Panel



will be used for reporting fluxes and forces. (Note that the units forDepth are set independently from the units for length in the Set Unitspanel.)

If you want to compute reference values from the conditions set on aparticular boundary zone, select the zone in the Compute From drop-down list. Note, however, that depending on the boundary conditionused, only some of the reference values may be set. For example, thereference length and area will not be set by computing the referencevalues from a boundary condition; you will need to set these manually.

To set the values manually, simply enter the value for each under theReference Values heading.

26.8.2 Setting the Reference Zone

If you are solving a flow involving multiple reference frames or slidingmeshes, you can plot velocities and other related quantities relative tothe motion of a specied \reference zone". Choose the desired zone in theReference Zone drop-down list. Changing the reference zone allows youto plot velocities (and total pressure, temperature, etc.) relative to themotion of dierent zones. See Chapter 9 for details about postprocessingof relative quantities.


26.9 Summary Reports of Case Settings

26.9 Summary Reports of Case Settings

You may sometimes nd it useful to get a report of the current settingsin your case. In FLUENT, you can list the settings for physical models,boundary conditions, material properties, and solver controls. This re-port allows you to get an overview of your current problem denitionquickly, instead of having to check the settings in each panel.

26.9.1 Generating a Summary Report

To generate a summary report you will use the Summary panel (Fig-ure 26.9.1).

Report !Summary...

Figure 26.9.1: The Summary Panel

The steps are as follows:

1. Select the information you would like to see in the report (Models,Boundary Conditions, Solver Controls, and/or Material Properties) inthe Report Options list.

2. To print the information to the FLUENT console window, click onthe Print button. To save the information to a text le, click onthe Save... button and specify the lename in the resulting SelectFile dialog box.


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