Twenty-Third Symposium on Naval Hydrodynamics (2001) / Chapter Skim
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Validation of Tab Assisted Control Surface Computation
Validation of Tab Assisted Control Surface Computation
Pages 474-484
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From page 474... ...
hr. bean developed The conh ol surfae consists of c stern stabilizer, c flap, ad c tab The m meri cl procedure is based on solvmg the mcomp~ Ale Rey olds~e~aad Na vier-Stokes equations coupled with several two~quation turbulence models Some fectmes of the m mericcl medhod used have been highlighted in particular, She preconditioning method, multig id method, Ed nom effecting far field bo mdary condition have been discussed The wall bo mdary condition for She specific dissipation rate which is impo t mt in obtammg good convergence for She At equation turbulence model have also been briefly discussed Computed results of the lif Ed d cg coefhcients of the conh ol surfae, flap torque coefficients Ed tab torque coefhcients et various Ogles of cttak of the stabilizer Ed of flap Ogles Ed tab angles hove been predicted within I O percent fi om the mecsmed values even et high Ogles of attack et I 5 deg es The discrepa ies of She torque coefhcients of flap Ed tab are somewhat higher particohr fly et high flax a d torque deflections Th re are two reasons for These higher discrepancies The fi st reason is that the turbulence models are i h re tly w ok m the flow regime where separation is severe, Ed the second is Nat the g id solution m both She flap Ed tab gap is not s fficient Th se will be She topics for future ir~stigatiom INTRODUCTION A contro I surfae h re will be defmed es consistmg of c tern stabilizer, c flap Ed c tab Th stabili:D:r may be fixed or movable but She flap Ed tab are always movable Conh ol smfa s have et least th ee major f motions applicable to both circmft Ed mane ~ehcles (1)
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From page 475... ...
Several c onvergence a cce lercti on tech i que s including multig id, local time pep, implicit residual smcothmg,pre33nditiomog mdbuk Viscosity dimpinghavebeenimpleme ted l o handle c omp sex geometry, She muhut lock g id structure is adopted Th se m merbal tech iqws have been implemented in a code tmed IFLOW, which is m abbreviation for incompressible FLOW IFLOW is i tended to be a production code for sol ring 2D, 3D, steady Ed msteady problems The code is highly mod par m structure se that different turbulence model s Ed higher order sch me. c m be easily implemented Some special features of She m merbal schemes us d will be highlighted Hew ver, deviled derivations will be mostly emitted Precorld dotted Method Th preconditioned method is developed based en a ystem of hyperbolic equaticus, but the idea goes back to th effc t to red t e She condition n mber
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From page 476... ...
, c=07 (10) 7hough mther tedious clg brcic m mipulations, fhe eig r~lues md lef md right eige functiom c m be fo md 7he maxim m of eiger~lues is used to define c local time step 7he eige f mctions re of no use to cenbal dffference chemes ex ept for e tablishmg c nomeflecting bo mdary condition et f r field 7he f nal system of equations to be solved m the conservative form is Since the fommulation is based on hyperbolic eq mion only, viscous terms should be cdded to fhe flw~es F
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From page 477... ...
cdvocated by Achie Br mdt [19] AchievingTME isanoble gocl, md will hav c sig iflcant impact on e gmeering cpplications of CFD Boundary Condfltions Only th solid wall md 6he f ufield boumdary conditions need to be discussed At 6he wall, the 6 ee components of v locity md 6he tu bulent kinetic energy rare set equ~l to :osro, 6he pressnu p is deriv d from cssumption th~t th pressu e g cdient normcl to th wall is :osro Finally, the wall boumdary condition of p ff iflc dis s ip at io n rcte m or igimdly giv n b y Wilcox p 148 m [10]
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From page 478... ...
and the tab hinge axis is at 9.70 in.. The entire control surface model is mounted on a pedestal to place the model outside of any test section boundary layer.
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From page 479... ...
en the flap md th tab The water turmel is not modeled m the computation A total of th ee meshes w re considered The coarse mesh consists of 112 28x20,44x8x8,8x8x12, md 8x8x12 g id cells for th first, second, thi d, md fourth block, rerpff tively This mesh consists of c total of Croat 65K g id cells Th medi m mesh doubles th member of g id cells in each curvilinear coordi me direction of each block md hr. c total m mber of g id cells of Croat half c million Th fme mesh will have the n mber of g id cells increased by 50 percent in each direction of ecchblock of She medi m mesh, gi ing c total m mber of g id cells of clout 1 6 millions it will be en that the solution obtained by the tine md She medi m mesh are almost identical, indicating that c g id mdependent solution hr3 been achieved Th bo mdary conditions imposed are the following The farfleld bo mdary conditions et both th upper md bWff wakes are zero g cdient for the thee components of the Cartesi m velocity, She turbulence q entities r md to md She nonretl - ting bo mdary condition for the pressure The nom flectmg bo mdary condition is import mt for go od convergence md accuracy es mentioned eafliff On She outflow bo mdary et She top of the computational domain are imposed fixed values for the 6 ee components of th Cartesi m velocity, th two turbulence q mtities r md en md ffO g cdient of the pressure Because of She presence of She pede till, the symmetric bo mdary condition is applied et the bottom of the computational domain Non-slip bo mdary condition for the velocity md zero g cdient for the pres mre are applied et the wall bo mdary The turbulent kinetic energy Wishes et She wall md the dissipation rare et She wall hr.
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From page 480... ...
The lift and drag coefficients will be defined as the total forces applied to the entire control surface. The flap torque coefficient will include both the torque applied to the flap and the tab while the tab torque coefficient will include the torque applied to the tab alone.
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From page 481... ...
A grid independent solution has not been achieved at high tab deflection, and the slope near zero tab deflection is much flatter than the measurement. The predicted slope of the tab torque coefficient near zero tab deflection seems to agree better with the measurement but the predicted torque coefficient at high tab deflection deviates from the measurement by more than 10%.
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From page 482... ...
Fehlner, " FreStream Characteristics of c Fcmily of Low-Aspect Rctio, All-Movable Conhol Suricces For Application to Ship Desigm", David Tcylor Model Bcsm R port 933, December 1958 4 Bow rs, Allen, " Wind Tunnel ~vestigation of th Characteristics of c Fkpped Control Suricce Mo mted on c Simulated Submarine Hull", University of Maryl md Wmd Tunne I R p ort N o 259, June, 1959 5 Ke win, Ju tine E, Philip Mmdel md S D m L wis, " A E pffimentcl Study of c Series of Fkpped Rndders", Journcl of Ship R search, December, 1972 6 Goodkich, G J
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From page 483... ...
md J C Strkw rdc, "Bo mdary Conditions for Subsonic Compressible Navier-Stokes Equations", Computers md Fluids, vol 9, pp 327-338, 1981 22 S mg, C H ,"A E plicit R mge-Kutta Medhod for 3D ~compressible Turbulent Flows", DTNSRDC/SH 1244-01, July 1987 23 Jcmeson, A md L Martinelli, "Mesh R fmement md Modeling Enors m Fluid Simoktion", AIAA Journal vol.
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From page 484... ...
et cl, "Development of Ballast Bulb for ACC Scilmg Yacht E peciclly for Ire anti - trion on Basic Low Drag Form," J Ksmsci Society of Naval A chitects, No 234, 2000,pp 51-59 AUTHOR'S REPLY Due to c relatively high turbulence level in c water tum 1, early experimental tests indicated that the flow was t rbulent et c Rey olds mmmber of cutout one million based on c me m chordlengfh of 9 53 inches For this reason, computations were made cssummg the fl w was completely t rbulent Tr msition from Icminar to turbulence was not considered Admittedly, turbulence models are not perfect for c complex flow ouches She one m.
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