Investigation of Aerodynamic Characteristics of Blended-Wing-Body Aircraft Based on Cluster System Guo-qing ZHANG 1; Shu-xing YANG1; Song-hai XUE1 Beijing Institute of Tecnology. Beijing100081,China e-mail: zhangguoqing@bit.edu.cn

Abstract:TheaerodynamiccharacteristicsoftheBWB-UAVweresimulatednumericallybasedontheHigh PerformanceComputingClusterSystem.Theeffectson theaerodynamiccharacteristicsofthewholeaircraft madebytheBWBwereinvestigated.The longitudinal/lateralcharacteristicsofBWBandthe conventional taillesssweep wing had been compared. The resultsshowedthatBWBconfigurationhadthebetter longitudinal aerodynamic characteristics. The causes of its excellentcharacteristicscanbeattributedtothenew wing-bodyliftingdesign,whichcanimprovetheflowing patternofthesurface.Butitslateralstabilitywasbad. Therefore,itwouldbeanimportantcriterionthattrying to enhance the lateral stability in BWB-UAV design. Keywords:BWB;ClusterSystem;sweepwing;stability; mesh .INTRODUCTION Inmoderntimes,thewarhasbecomemoreand more complicated.Wheneverycountryismakinggreat effortsinenhancingtheagilityandmaneuverabilityof theaircrafts,somenewaerodynamicdistributionsand configurationsaredrawingmoreandmoreattention. EspeciallytheBlendedWingBodyAircraft BWB Aircraft,becauseofitslighterqualityofthestructure, higherlift-dragratioandstrongerstealthfeatures,has drawnthefavorofmanydesigners.Exceptthese,the BWBdistributionhasthepotentialadvantagessuchas safety,comfortandenvironmentalnoise.SotheUnited States,Europe,Russiaandotheraviationindustryhave committed huge resources to conduct the study. U.S. led byBoeingcompaniesbringtheLangleyResearch CenterandStanfordUniversityandotherresearch institutionshadextensiveandin-depthstudyonthe BWB,involvingaerodynamic,structure,controland power,andotherdisciplines[1].Sincethe1990s,People haveahigherdemandonthestealthfeaturesandthe flight performance of the new generation combat aircraft (includingUAVs),removingverticaltailiseasierto meettheserequirements.SotheinvestigationofBWB-UAVshassetoffanupsurgeintheinternational aviation community. ThereareavarietyofBWB-UAVsprogramshave enteredtheflight-provenstage,suchasX45X47AB.Butinourcountry,theinvestigationsof aerodynamic characteristics of the tandem wing are very scarce;especiallytheeffectsontheaerodynamic characteristicsofthewholeaircraftmadebyBWB configurationaremoreworthyofdeepinvestigation. ThispaperhadusedthematurenumericalCFD software,theverticalandhorizontalaerodynamic characteristicsoftwotaillessconfigurationsofthe wholeaircrafthadbeensimulatednumericallyand drawn some corresponding conclusions..CLUSTER SYSTEM Becauseitisaerodynamicsimulationofthewhole aircraft.Theamountofmeshgenerationhasreached over 200 million. Ordinary computer and a single server memoryhavebeenunabletomeetitsaccuracyand feasibilityoftherequests.Sothisexperimentwas operated on CFD numerical platform in the use of high-performanceclustersystemstructuredwithparallel clusterarchitecture.Thissystemisconfiguredwith36 Itanium2processors;Calculationofnetworkis configuredwith24interfaceinfinibandofone switchboard.Networkmanagementisequippedwith 3Com 100M 24 interface infiniband of one switchboard. Theoreticalcalculationofpeakcanreach230.4Glops. (Glops is 10 billion calculation per second) ..CFD A.Size Function and Grid of Technology Fig.1 The structural (outside) and non-structural grids of the whole numerical zones Inmodelingofthewholeaircraft,thequalityand size of the mesh generation will often directly affect the accuracyoftheexperimentalresults.Butthekey technology which affects the quality and quantity of the grids generation is to control and grasp size of the grid. Basedonthis,duringmeshingthenon-structuralgrids of the wing and tail, the experiment took the method of size function control grid size [2]. (It doesnt changethe entirestructureofthenetworktopology)Asshownin Fig.1, the parts of grid are refined for the whole aircraft, enhancing the accuracy of the experiment. B.The Model and Setting of the Boundary Conditions Thisstudyusedtheaerodynamicshapedesign whichwasthesameasX-47B,asshowninFig.2;the geometricparameterswereshownasfollows:wing (TrapezoidalWing),L=2.4m,bAg=0.173m, S=0.415m2, =13.87,1 =17.950. Fig.2 Comparison of the BWB and conventional tailless configuration Thevelocityofinletisset0.3Mach,Re610 06 . 1 ,duringthenumericalsimulation,pressure is greater, so it is set relative pressure. The temperature is300K,usingcouple-implicitsolver.Thesimulation usesK turbulencemodel,SIMPLEIterationand uses wall functions. . THE EXPERIMENTAL RESULTS AND ANALYSIS A.The Impacts on the Longtitudinal Aerodynamic Characteristics Made by BWB FromtheFigswecansee,thelongitudinal aerodynamiccharacteristicsofBWBhadbeen improvedobviously,CL(15 )hadincreasedabout 84.27,Cmax Lis48.74,butC0 xhadnoobvious changes,AndthestallcharacteristicsoftheBWB become more flat, compared to the conventional tailless distribution,ithadbeenimprovedsignificantly.And the 0zlmc