1,722,103 research outputs found
Development of a novel fully coupled solver in OpenFOAM: Steady-state incompressible turbulent flows
No full textIn this work a block coupled algorithm for the solution of three-dimensional incompressible turbulent flows is presented. A cell-centered finite-volume method for unstructured grids is employed. The interequation coupling of the incompressible Navier-Stokes equations is obtained using a SIMPLE-type algorithm with a Rhie-Chow interpolation technique. Due to the simultaneous solution of momentum and continuity equations, implicit block coupling of pressure and velocity variables leads to faster convergence compared to classical, loosely coupled, segregated algorithms of the SIMPLE family of algorithms. This gain in convergence speed is accompanied by an improvement in numerical robustness. Additionally, a two-equation eddy viscosity turbulence model is solved in a segregated fashion. The substnatially improved performance of the block coupled approach compared to the segregated approach is demonstrated in a set of test cases. It is shown that the scalability of the coupled solution algorithm with increasing numbers of cells is nearly linear. To achieve this scalability, an algebraic multigrid solver for block coupled systems of equations has been implemented and used as linear solver for the system of block equations. The presented algorithm has been entirely embedded into the leading open-source computational fluid dynamics (CFD) library OpenFOAM. © 2014 Taylor and Francis Group, LLC.Benzi M, 2005, ACT NUMERIC, V14, P1, DOI 10.1017-S0962492904000212; Brandt A., 1977, MATH COMPUT; Casartelli E., 2012, INT C EXH INN APPR G; DACLESMARIANI J, 1995, AIAA J, V33, P1561, DOI 10.2514-3.12826; Darwish M., 2001, NUMER HEAT TRANSFE B; Darwish M., 2000, INT J NUMER METH FLU; Darwish M., 2003, INT J HEAT MASS TRAN; Darwish M., 2008, J COMPUT PHYS; Darwish M., 2004, NUMER HEAT TRANSFE B; de Lemos MJS, 2000, NUMER HEAT TR B-FUND, V37, P489; Doormaal J. V., 1986, NAT HEAT TRANSF C DE; Doormaal J. V., 1984, NUMER HEAT TRANSFER; Federenko R., ZH VYCHISL MAT MAT F, P922; Ferziger J., 1994, COMPUTATIONAL METHOD; Hutchinson B., 1986, NUMER HEAT TRANSFER; Keller S., 2004, P 10 BRAZ C THERM SC; Laia Y. G., 1997, NUMER HEAT TRANSFE B, V32, P267; Menter F., 1994, AIAA J; Menter F. R., 2003, TURBULENCE HEAT MASS; Moukalled F., 2000, NUMER HEAT TRANSFE B; Muzaferija S., 1994, THESIS U LONDON LOND; Patankar S., 1972, INT J HEAT MASS TRAN; Patankar S. V., 1980, NUMERICAL HEAT TRANS; Poussin F., 1968, SIAM J NUMER ANAL; Rhie C., 1983, AIAA J; Singh D., 2013, NUMER HEAT TRANSFE A; Vradis C., 1998, NUMERICAL HEAT TRANS, V33, P79; Weller H., 1998, COMPUT PHYS; Woodfield PL, 2003, NUMER HEAT TR B-FUND, V43, P403, DOI 10.1080-104077903901221223
A pressure-based framework for the resolution of multi-fluid flow problems
No full textPressure-based methods represent a class of Computational Fluid Dynamics (CFD) algorithms in which pressure, rather than density, is used as a principal variable. This paper presents a review of segregated pressure-based methods and reports on a newly developed fully coupled method for the solution of multi-fluid flow problems. Results indicate the superiority of the coupled solver over the segregated approach. © 2013 AIP Publishing LLC.CARVER MB, 1984, J FLUID ENG-T ASME, V106, P147; Darwish M., 2009, J COMPUT PHYS, V28, P180; Darwish M., 2011, ICNAAM 2011 HALK GRE; HARLOW FH, 1975, J COMPUT PHYS, V17, P19, DOI 10.1016-0021-9991(75)90061-3; Moukalled F, 2004, NUMER HEAT TR B-FUND, V45, P495, DOI 10.1080-10407790490430651; Moukalled F, 2004, NUMER HEAT TR B-FUND, V45, P523, DOI 10.1080-10407790490437997; Moukalled F., 2001, NUMER HEAT TRANSFE B, V40, P99; Moukalled F., 2006, HDB NUMERICAL HEAT T, P325; RHIE CM, 1983, AIAA J, V21, P1525, DOI 10.2514-3.8284; Spalding D.B, 1976, HTS7611 IMP COLL0
A fully coupled navier-stokes solver for fluid flow at all speeds
No full textThis article deals with the formulation and testing of a newly developed, fully coupled, pressure-based algorithm for the solution of fluid flow at all speeds. The new algorithm is an extension into compressible flows of a fully coupled algorithm developed by the authors for laminar incompressible flows. The implicit velocity-pressure-density coupling is resolved by deriving a pressure equation following a procedure similar to a segregated SIMPLE algorithm using the Rhie-Chow interpolation technique. The coefficients of the momentum and continuity equations are assembled into one matrix and solved simultaneously, with their convergence accelerated via an algebraic multigrid method. The performance of the coupled solver is assessed by solving a number of two-dimensional problems in the subsonic, transsonic, supersonic, and hypersonic regimes over several grid systems of increasing sizes. For a desired level of convergence, results for each problem are presented in the form of convergence history plots, tabulated values of the maximum number of required iterations, the total CPU time, and the CPU time per control volume. © 2014 Taylor and Francis Group, LLC.Abbasi R, 2013, COMPUT FLUIDS, V81, P68, DOI 10.1016-j.compfluid.2013.03.014; Acharya S, 2007, J HEAT TRANS-T ASME, V129, P407, DOI 10.1115-1.2716419; Anderson Jr J.D., 1982, MODERN COMPRESSIBLE; Anjorin V. A. O., 2001, INT J FLUID DYNAM, V5, P59; Barton IE, 1998, INT J NUMER METH FL, V26, P459, DOI 10.1002-(SICI)1097-0363(19980228)26:4459::AID-FLD6453.0.CO;2-U; BATINA JT, 1991, AIAA J, V29, P1836, DOI 10.2514-3.10808; Blokhin AM, 2009, SB MATH+, V200, P157, DOI 10.1070-SM2009v200n02ABEH003990; Cabboussat A., 2005, J COMPUT PHYS, V203, P626; Caretto L. S., 1972, Computer Methods in Applied Mechanics and Engineering, V1, DOI 10.1016-0045-7825(72)90020-5; Darwish M, 2001, NUMER HEAT TR B-FUND, V40, P99; Darwish M, 2007, NUMER HEAT TR B-FUND, V52, P353, DOI 10.1080-10407790701372785; Darwish M, 2004, NUMER HEAT TR B-FUND, V45, P49, DOI 10.1080-1040779049025487; Darwish M, 2009, J COMPUT PHYS, V228, P180, DOI 10.1016-j.jcp.2008.08.027; DEMIRDZIC I, 1993, INT J NUMER METH FL, V16, P1029, DOI 10.1002-fld.1650161202; Deng GB, 2001, COMPUT FLUIDS, V30, P445, DOI 10.1016-S0045-7930(00)00025-6; Dettmer W, 2006, COMPUT METHOD APPL M, V195, P3038, DOI 10.1016-j.cma.2004.07.057; Elling V, 2008, COMMUN PUR APPL MATH, V61, P1347, DOI 10.1002-cpa.20231; Favini B, 1996, INT J NUMER METH FL, V23, P589, DOI 10.1002-(SICI)1097-0363(19960930)23:6589::AID-FLD4443.3.CO;2-R; Grismer M. J., 1994, THESIS NOTRE DAME U; Hirsch C., 1990, NUMERICAL COMPUTATIO; HWANG CJ, 1993, AIAA J, V31, P61, DOI 10.2514-3.11319; Karlci K. C., 1986, THESIS U MINNESOTA; Khalid M. S., 2009, P WORLD C ENG 2009 W; Kissling K., 2010, 5 EUR C COMP FLUID D; Langtry RB, 2005, 2005522 AIAA; LIEN FS, 1993, J FLUID ENG-T ASME, V115, P717, DOI 10.1115-1.2910204; LIEN FS, 1994, COMPUT METHOD APPL M, V114, P123, DOI 10.1016-0045-7825(94)90165-1; MARCHI CH, 1994, NUMER HEAT TR B-FUND, V26, P293, DOI 10.1080-10407799408914931; Menter F, 2003, TURBULENCE HEAT MASS, V4, P2003; Modesto-Madera N. A., 2010, THESIS RENSSELAER PO; Moguen Y, 2013, J COMPUT APPL MATH, V246, P136, DOI 10.1016-j.cam.2012.10.029; Montero R. S., 2000, 200027 NASA ICASE; Moukalled F, 2003, J COMPUT PHYS, V190, P550, DOI 10.1016-S0021-9991(03)00297-3; Moukalled F, 2004, NUMER HEAT TR B-FUND, V45, P343, DOI 10.1080-10407790490268841; Darwish M, 2003, INT J NUMER METH FL, V41, P1221, DOI 10.1002-fld.490; Moukalled F, 2000, NUMER HEAT TR B-FUND, V37, P103; Moukalled F, 2002, NUMER HEAT TR B-FUND, V42, P259, DOI 10.1080-10407790190053941; Moukalled F, 2001, J COMPUT PHYS, V168, P101, DOI 10.1006-jcph.2000.6683; Muzaferija S, 1997, J COMPUT PHYS, V138, P766, DOI 10.1006-jcph.1997.5853; PATANKAR SV, 1972, INT J HEAT MASS TRAN, V15, P1787, DOI 10.1016-0017-9310(72)90054-3; Rhie C., 1983, AIAA J, V17, P1525; Rispoli F., 2009, ASME J APPL MECH, V76, DOI [10.1115-1.3062969, DOI 10.1115-1.3062969]; Rossow CC, 2007, J COMPUT PHYS, V220, P879, DOI 10.1016-j.jcp.2006.05.034; Shapiro A. H., 1953, DYNAMICS THERMODYNAM; Shapiro E, 2005, J COMPUT PHYS, V210, P584, DOI 10.1016-j.jcp.2005.05.001; Shterev KS, 2010, J COMPUT PHYS, V229, P461, DOI 10.1016-j.jcp.2009.09.042; Tao WQ, 2004, NUMER HEAT TR B-FUND, V45, P1, DOI 10.1080-1040779049025485; Tezduyar TE, 2006, COMPUT MECH, V38, P469, DOI 10.1007-s00466-005-0025-6; VANDOORMAAL JP, 1984, NUMER HEAT TRANSFER, V7, P147, DOI 10.1080-10407798408546946; van Wachem B. G. M., 2006, EUR C COMP FLUID DYN; van Wachem B. G. M., 2007, 6 INT C MULT FLOW IC; Yaldin Y., 1991, AIAA J, V29, P712; Yang JY, 2001, AIAA J, V39, P2082, DOI 10.2514-2.1231; ZHANG LX, 2011, J HYDRODYN, V23, P421
Convective schemes for capturing interfaces of free-surface flows on unstructured grids
No full textIn this article, the general methodology used in constructing interface-capturing schemes is clarified and concisely described. Moreover, a new interface-capturing scheme, denoted STACS and based on a switching strategy, is developed. The accuracy of the new scheme is compared to the well-known CICSAM and HRIC schemes by solving four pure advection test problems. Results, displayed in the form of interface contours for the various schemes, reveal deterioration in the accuracy of the CICSAM and HRIC schemes, with their performance approaching that of the UPWIND scheme as the Courant number increases. On the other hand, predictions obtained with the new STACS scheme are by far more accurate and less diffusive, preserving interface sharpness and boundedness at all Courant number values considered.BRACKBILL JU, 1992, J COMPUT PHYS, V100, P335, DOI 10.1016-0021-9991(92)90240-Y; BRANDT A, 1977, MATH COMPUT, V31, P333; Cleary PW, 2000, INT J CAST METAL RES, V12, P357; Darwish M, 1996, COMPUT METHOD APPL M, V129, P221, DOI 10.1016-0045-7825(95)00881-0; Darwish M, 2001, NUMER HEAT TR B-FUND, V40, P99; Darwish M, 2000, NUMER HEAT TR B-FUND, V37, P227; DARWISH M, 2000, P 36 AIAA ASME SAE A; DARWISH M, 2002, P IASTED INT C APPL; Darwish MS, 1998, NUMER HEAT TR B-FUND, V34, P191, DOI 10.1080-10407799808915054; Darwish MS, 2003, INT J HEAT MASS TRAN, V46, P599, DOI 10.1016-S0017-9310(02)00330-7; DARWISH MS, 1993, NUMER HEAT TR B-FUND, V24, P353, DOI 10.1080-10407799308955898; Ha J., 1999, P 2 INT C CFD MIN PR; HARLOW FH, 1971, LA4700 LASA; Harvie DJE, 2001, INT J NUMER METH FL, V35, P151, DOI 10.1002-1097-0363(20010130)35:2151::AID-FLD873.0.CO;2-4; HIRT CW, 1981, J COMPUT PHYS, V39, P201, DOI 10.1016-0021-9991(81)90145-5; Jasak H, 1996, THESIS TECHNOLOGY ME; Kothe D B, 1999, P 3 ASME JSME JOINT; KOTHE DB, 1992, AIAA J, V30, P2694, DOI 10.2514-3.11286; LAFAURIE B, 1994, J COMPUT PHYS, V113, P134, DOI 10.1006-jcph.1994.1123; LEONARD BP, 1990, COMPUT METH APPL MEC, P59; LEONARD BP, 1991, COMPUT FLUIDS, V19, P141, DOI 10.1016-0045-7930(91)90011-6; LEONARD BP, 1990, INT J NUMER METH ENG, V30, P729, DOI 10.1002-nme.1620300412; LEONARD BP, 1991, COMPUT METHOD APPL M, V88, P17, DOI 10.1016-0045-7825(91)90232-U; Maronnier V, 1999, J COMPUT PHYS, V155, P439, DOI 10.1006-jcph.1999.6346; Darwish M, 2003, INT J NUMER METH FL, V41, P1221, DOI 10.1002-fld.490; MOUKALLED F, 1996, NUMER HEAT TRANSFE B, V31, P91; Moukalled F, 2001, J COMPUT PHYS, V168, P101, DOI 10.1006-jcph.2000.6683; Moukrim A, 2003, RAIRO-OPER RES, V37, P1, DOI 10.1051-ro:2003011; Muzaferija S, 1998, P 22 S NAV HYDR WASH, P638; Muzaferija S, 1998, NONLINEAR WATER WAVE, P59; Nichols B., 1980, LA8355; Nichols B.D., 1975, P 1 INT C NUM SHIP H; Noh W. F., 1976, LECTURE NOTES PHYSIC, V59, P330; OSHER S, 1983, J COMPUT PHYS, V50, P447, DOI 10.1016-0021-9991(83)90106-7; Puckett EG, 1991, P 4 INT S COMP FLUID, P933; RAMSHAW JD, 1976, J COMPUT PHYS, V21, P438, DOI 10.1016-0021-9991(76)90039-5; Renardy Y, 2002, J COMPUT PHYS, V183, P400, DOI 10.1006-jcph.2002.7190; Rhie C.M., 1986, 860207 AIAA; Rider WJ, 1998, J COMPUT PHYS, V141, P112, DOI 10.1006-jcph.1998.5906; RIDER WJ, 1995, P 12 AIAA CFD C SAN; Rudman M, 1997, INT J NUMER METH FL, V24, P671, DOI 10.1002-(SICI)1097-0363(19970415)24:7671::AID-FLD5083.0.CO;2-9; SHYY W, 1988, 883566CP AIAA; SHYY W, 1992, AIAA J, V30, P2660, DOI 10.2514-3.11282; Ubbink O, 1999, J COMPUT PHYS, V153, P26, DOI 10.1006-jcph.1999.6276; UNVERDI SO, 1992, J COMPUT PHYS, V100, P25, DOI 10.1016-0021-9991(92)90307-K; YOUNGS DL, 1984, 449235 AT WEAP RES E; ZALESAK ST, 1979, J COMPUT PHYS, V31, P335, DOI 10.1016-0021-9991(79)90051-223252
Performance comparison of the NWF and DC methods for implementing High-Resolution schemes in a fully coupled incompressible flow solver
No full textThis paper reports on the use of the Normalized Weighting Factor (NWF) method and the Deferred Correction (DC) approach for the implementation of High Resolution (HR) convective schemes in an implicit, fully coupled, pressure-based flow solver. Four HR schemes are realized within the framework of the NWF and DC methods and employed to solve the following three laminar flow problems: (i) lid-driven flow in a square cavity, (ii) sudden expansion in a square cavity, and (iii) flow in a planar T-junction, over three grid systems with sizes of 104, 5 × 104, and 3 × 105 control volumes. The merit of both approaches is demonstrated by comparing the computational costs required to solve these problems using the various HR schemes on the different grid systems. Whereas previous attempts to use the NWF method in a segregated flow solver failed to produce converged solutions, current results clearly demonstrate that both methods are suitable for utilization in a coupled flow solver. In terms of CPU efficiency, there is no global and consistent superiority of any method over another even though the DC method outperformed the NWF method in two of the three test problems solved. © 2010 Elsevier Inc. All rights reserved.BRAATEN ME, 1985, THESIS U MINNESOTA; Caretto L. S., 1972, Computer Methods in Applied Mechanics and Engineering, V1, DOI 10.1016-0045-7825(72)90020-5; Chakravarthy S. R., 1983, 831943 AIAA; Darwish M, 2007, NUMER HEAT TR B-FUND, V52, P353, DOI 10.1080-10407790701372785; Darwish M., 2009, J COMPUT PHYS, V28, P180; Darwish MS, 1996, NUMER HEAT TR B-FUND, V30, P217, DOI 10.1080-10407799608915080; GASKELL PH, 1988, INT J NUMER METH FL, V8, P617, DOI 10.1002-fld.1650080602; HARTEN A, 1983, J COMPUT PHYS, V49, P357, DOI 10.1016-0021-9991(83)90136-5; HAYES RE, 1989, COMPUT FLUIDS, V17, P537, DOI 10.1016-0045-7930(89)90027-3; KARKI KC, 1990, INT J NUMER METH FL, V11, P1, DOI 10.1002-fld.1650110102; LEONARD BP, 1979, COMPUT METHOD APPL M, V19, P59, DOI 10.1016-0045-7825(79)90034-3; LEONARD BP, 1988, INT J NUMER METH FL, V8, P1291, DOI 10.1002-fld.1650081013; LEONARD BP, 1990, INT J NUMER METH ENG, V30, P729, DOI 10.1002-nme.1620300412; Mazhar Z, 2001, NUMER HEAT TR B-FUND, V39, P91, DOI 10.1080-104077901460704; Moukalled F, 2000, NUMER HEAT TR B-FUND, V37, P103; PATANKAR SV, 1972, INT J HEAT MASS TRAN, V15, P1787, DOI 10.1016-0017-9310(72)90054-3; RHIE CM, 1983, AIAA J, V21, P1525, DOI 10.2514-3.8284; Rubin S., 1982, J COMPUT PHYS, V27, P153; SHYY W, 1985, J COMPUT PHYS, V57, P415, DOI 10.1016-0021-9991(85)90188-3; SYE S, 1985, NASACR174776; van Leer B., 1977, J COMPUT PHYS, V23, P101; VANKA SP, 1986, J COMPUT PHYS, V65, P138, DOI 10.1016-0021-9991(86)90008-212
A coupled finite volume solver for the solution of incompressible flows on unstructured grids
No full textThis paper reports on a newly developed fully coupled pressure-based algorithm for the solution of laminar incompressible flow problems on collocated unstructured grids. The implicit pressure-velocity coupling is accomplished by deriving a pressure equation in a procedure similar to a segregated SIMPLE algorithm using the Rhie-Chow interpolation technique and assembling the coefficients of the momentum and continuity equations into one diagonally dominant matrix. The extended systems of continuity and momentum equations are solved simultaneously and their convergence is accelerated by using an algebraic multigrid solver. The performance of the coupled approach as compared to the segregated approach, exemplified by SIMPLE, is tested by solving five laminar flow problems using both methodologies and comparing their computational costs. Results indicate that the number of iterations needed by the coupled solver for the solution to converge to a desired level on both structured and unstructured meshes is grid independent. For relatively coarse meshes, the CPU time required by the coupled solver on structured grid is lower than the CPU time required on unstructured grid. On dense meshes however, this is no longer true. For low and moderate values of the grid aspect ratio, the number of iterations required by the coupled solver remains unchanged, while the computational cost slightly increases. For structured and unstructured grid systems, the required number of iterations is almost independent of the grid size at any value of the grid expansion ratio. Recorded CPU time values show that the coupled approach substantially reduces the computational cost as compared to the segregated approach with the reduction rate increasing as the grid size increases. © 2008 Elsevier Inc. All rights reserved.Ammara I, 2004, INT J NUMER METH FL, V44, P621, DOI 10.1002-fld.662; Brufau P, 2003, J COMPUT PHYS, V186, P503, DOI 10.1016-S0021-9991(03)00072-X; BRAATEN ME, 1985, THESIS U MINNESOTA; Brandt A., 1977, Mathematics of Computation, V31, DOI 10.2307-2006422; Caretto L. S., 1972, Computer Methods in Applied Mechanics and Engineering, V1, DOI 10.1016-0045-7825(72)90020-5; CHORIN AJ, 1968, MATH COMPUT, V22, P745, DOI 10.2307-2004575; Darwish M, 2001, NUMER HEAT TR B-FUND, V40, P99; Darwish M, 2007, NUMER HEAT TR B-FUND, V52, P353, DOI 10.1080-10407790701372785; Darwish MS, 1996, NUMER HEAT TR B-FUND, V30, P217, DOI 10.1080-10407799608915080; DARWISH MS, 1994, NUMER HEAT TR B-FUND, V26, P79, DOI 10.1080-10407799408914918; Deng GB, 2001, COMPUT FLUIDS, V30, P445, DOI 10.1016-S0045-7930(00)00025-6; Elias SR, 1997, INT J NUMER METH ENG, V40, P887; Fedorenko R P, 1962, USSR COMP MATH MATH, V1, P1092, DOI 10.1016-0041-5553(62)90031-9; GALPIN PF, 1986, NUMER HEAT TRANSFER, V10, P105, DOI 10.1080-10407798608552499; Hanby RF, 1996, INT J NUMER METH FL, V22, P353; HARLOW FH, 1965, PHYS FLUIDS, V8, P2182, DOI 10.1063-1.1761178; HAYES RE, 1989, COMPUT FLUIDS, V17, P537, DOI 10.1016-0045-7930(89)90027-3; HUTCHINSON BR, 1986, NUMER HEAT TRANSFER, V9, P511, DOI 10.1080-10407798608552152; KARKI KC, 1990, INT J NUMER METH FL, V11, P1, DOI 10.1002-fld.1650110102; LANSDALE RD, 1991, NUMERICAL METHOD L 2, V7, P1432; Mazhar Z, 2001, NUMER HEAT TR B-FUND, V39, P91, DOI 10.1080-104077901460704; Moukalled F, 2003, J COMPUT PHYS, V190, P550, DOI 10.1016-S0021-9991(03)00297-3; Darwish M, 2003, INT J NUMER METH FL, V41, P1221, DOI 10.1002-fld.490; Moukalled F, 2000, NUMER HEAT TR B-FUND, V37, P103; Moukalled F, 2001, J COMPUT PHYS, V168, P101, DOI 10.1006-jcph.2000.6683; Moukalled F., 2006, HDB NUMERICAL HEAT T, P325; Moukalled F, 2003, NUMER HEAT TR A-APPL, V43, P543, DOI 10.1080-10407780390122808; Pascau A, 1996, COMMUN NUMER METH EN, V12, P617, DOI 10.1002-(SICI)1099-0887(199610)12:10617::AID-CNM103.3.CO;2-A; Patankar S. V., 1981, NUMERICAL HEAT TRANS; PATANKAR SV, 1972, INT J HEAT MASS TRAN, V15, P1787, DOI 10.1016-0017-9310(72)90054-3; POMMERELL C, 1994, SIAM J SCI COMPUT, V15, P460, DOI 10.1137-0915031; POUSSIN FD, 1968, SIAM J NUMER ANAL, V5, P340; RHIE CM, 1983, AIAA J, V21, P1525, DOI 10.2514-3.8284; RODI W, 1989, COMPUT METHOD APPL M, V75, P369, DOI 10.1016-0045-7825(89)90037-6; Rubin S., 1982, J COMPUT PHYS, V27, P153; SCHNEIDER GE, 1978, NUMERICAL METHODS LA; VANDOORMAL JP, 1985, THESIS U WATERLOO ON; VANKA SP, 1986, J COMPUT PHYS, V65, P138, DOI 10.1016-0021-9991(86)90008-2; WEBSTER R, 1994, INT J NUMER METH FL, V18, P761, DOI 10.1002-fld.165018080525191
Numerical analysis of the gas-assisted laser cutting flow from various supersonic nozzles
No full textIn the present paper, the exit jet patterns from four different supersonic nozzles have been numerically simulated using OpenFOAM® Computational Fluid Dynamics (CFD) toolbox. The desired-design operating condition, for each of these nozzles, has been calculated using quasi 1-D gas dynamics theory. Mach number and pressure distributions are presented for each nozzle to illustrate the effect of both the nozzle geometry and the operating conditions on the behaviour of the exit jet. Then, the predicted numerical results have been validated by comparison with the experimental measurements reported in previous literature. As main outcomes, the simulations results are quantitatively in high agreement with the reported experimental observations. The correlations between jet flow stability and divergence angle are discussed and the effect of Mach number and exit diameter on the jet divergence are presented
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Transient schemes for capturing interfaces of free-surface flows
No full textThis article presents a new methodology for the development of Transient Interpolation for Capturing of Surfaces schemes suitable for the simulation of free-surface flows, which is given the acronym TICS. The newly developed approach is based on a switching strategy that combines a bounded high-order transient scheme with a bounded compressive transient scheme. Bounded high-order and compressive transient schemes are constructed by discretizing the transient term in the volume-of-fluid (r) equation over a temporal control-volume in a way similar to the discretization of the convection term over a spatial control-volume, allowing advances in building convective schemes to be exploited in the development of bounded high-order and compressive transient schemes. Following that approach, a bounded version of the second-order upwind Euler scheme is constructed (B-SOUE). The B-SOUE is used to develop a family of temporal compressive schemes that is denoted by the B-CE m family, where m refers to the slope of the scheme on a temporal normalized variable diagram. The TICS methodology is then applied to the B-SOUE scheme and the B-CE m family of schemes to create a new family of transient interface-capturing schemes that is designated by TICS m. The virtues of the TICS m family, in producing a steep interface for the volume-of-fluid (r) field that defines the volume fraction occupied by the different fluids in a computational domain, are demonstrated through results generated using two schemes of the family (TICS 1.75 and TICS 2.5). The accuracy of the new transient TICS schemes is compared to the first-order Euler scheme, the Crank-Nicolson scheme, and the B-SOUE scheme by solving four pure advection test problems (advection of hollow shapes in an oblique flow field and advection of a solid body in a rotational flow field) and one flow problem (the break of a dam) using both the SMART and the STACS convective schemes. 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