Numerična obravnava problema aerodinamike vozil : magistrsko delo /
Obravnavali smo problem turbulentnega toka nestisljive viskozne tekočine v kanalih in okoli ovir. Reynoldsove enačbe smo zaključili z dvoenačbnim turbulentnim modelom in upoštevali vpliv trdnih sten z različnimi dušilnimi funkcijami. Odločili smo se za tri različne modele dušilnih funkcij: za Lam-Br...
Shranjeno v:
| Glavni avtor: | |
|---|---|
| Drugi avtorji: | |
| Format: | Thesis Knjiga |
| Jezik: | Slovenian |
| Izdano: |
Maribor :
[Z. Žunič],
1997.
|
| Teme: | |
| Oznake: |
Označite
Brez oznak, prvi označite!
|
| Izvleček: | Obravnavali smo problem turbulentnega toka nestisljive viskozne tekočine v kanalih in okoli ovir. Reynoldsove enačbe smo zaključili z dvoenačbnim turbulentnim modelom in upoštevali vpliv trdnih sten z različnimi dušilnimi funkcijami. Odločili smo se za tri različne modele dušilnih funkcij: za Lam-Bremhorstov, Naganov in Fan-Lakshminarayana-Barnettov model. Sistem parcialnih diferencialnih enačb osnovnih zakonov ohranitve smo reševali z diskretno metodo končnih volumnov. Kontinuitetno in gibalni enačbi smo povezali z uporabo principa umetne stisljivosti. Konvektivne tokove smo računali po metodi karakteristik, difuzijske tokove in izvorne člene pa s končnimi razlikami (upwind in centralnimi končnimi razlikami). Za napredovanje po času smo uporabili eksplicitno metodo Runge-Kutta četrtega reda. Natančnost in konvergenco uporabljene metode smo preizkusili na preprostih primerih laminarnega toka. Izračunali smo tok v gnani kotanji, tok v kanalu s stopnico in tok skozi nenadno simetrično razširitev. Turbulentne modele smo testirali na primeru razvitega toka v kanalu, razvoja turbulentne mejne plasti v kanalu in toka v kanalu s stopnico. Testni primeri so nam služili kot ocena natančnosti in učinkovitosti uporabljene numerične metode ter kot kriterij za izbiro najustreznejšega turbulentnega modela. Zaključni primer je bil izračun tokovnega polja okoli avtobusa mestnega prometa ter izračun količnika zračnega upora. The aim of contribution is the study of turbulent uncompressible viscous fluid flow in channels and around obstacles. Reynolds equations have been closed by two-equation turbulence model. Dumping functions were used to account for solid walls effect. Theree different turbulence models have been used: Lam-Bremhorst's, Nagano's and Fan-Lakshminarayana-Barnett's model. The system of partial differential equations has been solved by finite volume method. For coupling the continuity and momentum equations, the artificial compressibility formulation was employed. The characteristics based method (CBM) was used for discretization of the convective fluxes and finite differences for discretization of the viscous fluxes and source terms (upwind and central finite differences). For the time integration the explicit fourth-order Runge-Kutta time stepping method was employed. The simple laminar flows were used for testing of accuracy and convergence of the method. Driven cavity, channel with backward facing step and channel with sudden expansion were calculated. Turbulence models have been tested on fully developed channel flow, developing turbulent boundary layer in channel and backward facing step flow. Test cases have been used for assesment of accuracy and efficiency of the numerical method adn as a criterium to choose the most apropriate turbulence model. The last case was calculation of flow field around city traffic bus and calculation of drag coefficient. |
|---|---|
| Fizični opis: | X, 83 f. : graf. prikazi ; 30 cm. |