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COB236 Supersonic Flow Over a Spike-Nosed Body of Revolution
Algacyr Morgenstern Jr.
Divisão de Sistemas Espaciais - CTA/Instituto de Aeronáutica e Espaço
CEP 12228-904 São José dos Campos, SP, Brasil - E-mail: algacyr@ase-n2.iae.cta.br
The unsteady, viscous, supersonic flow over a spike-nosed body of revolution was numerically investigated by solving the Navier-Stokes equations. The time-accurate computations were performed employing an implicit algorithm based on the second-order time accurate LU-SGS scheme with the incorporation of a subiteration procedure to maintain time accuracy. Self-sustained oscillations for a Mach number of 3.0 and Reynolds number of 7.87 x 106/m were observed in the numerical computations, for a spike length to shoulder height ratio of 1.74, confirming the experimental result. The numerical result predicted correctly the discrete frequency range as well as the sound pressure intensities. The flow structure is also presented and discussed.
Keywords: unsteady flow; supersonic flow; spike-nosed body; time-accurate computations; Newton-like subiterations.
COB335 PRESSURE-BASED SOLUTION FOR THE RADIAL STOKES FLOWS: VALIDATION AND PROPERTIES
Jáuber C. Oliveira and Cristina H. Amon
Mechanical Engineering Department - Carnegie Mellon University, Pittsburgh, PA 15213
E-mails: jo2p+@andrew.cmu.edu and camon+@andrew.cmu.edu
A novel pressure-based methodology is proposed and implemented to approximate the solution of the partial differential equations that model radial Stokes flows between two parallel disks. Eigenfunction expansions and Green’s function representations are combined to obtain directly the pressure distribution for a variety of inflow boundary conditions. The velocity field is accurately recovered from the pressure distribution. This methodology was implemented numerically and validated with both exact solutions and numerical spectral element results. By exploring the analytical characteristics of the method, we extract additional information on the behavior of the solution in terms of the inflow functions and we prove rigorously the existence and uniqueness of solutions.
Keywords: pressure-based, radial Stokes flow, Green’s functions, eigenfunctions
COB545 DIRECTED-ENERGY AIR SPIKE INLET AT MACH 10 WITH 15-25 kW ARC POWER
P.G.P. Toro, H.T. Nagamatsu, L.N. Myrabo
Department of Mechanical Engineering, Aeronautical Engineering and Mechanics, Rensselaer Polytechnic Institute, Troy, NY 12180-3590 - USA, torop@rpi.edu, nagamh@rpi.edu, myrabl@rpi.edu
The use of thermal energy as a means of enhancing flight performance of blunt bodies at hypersonic speeds is investigated. The "Directed-Energy Air Spike" (DEAS) inlet concept proposes the beamed transmission of concentrated energy forward of a moving vehicle in order to change the bow shock configuration from a detached normal (strong) shock wave to an oblique, parabolic-shaped (weak) shock wave. This new approach provides low aerodynamic drag and heating, or also deflects the oncoming air into an annular hypersonic inlet. The compressed inlet air can either be accelerated to produce thrust or decelerated to extract onboard electric power. A 6-in. diameter blunt body model was fabricated and pressure transducers are installed at its surface and equipped with 6-in. long slender plasma torch at the stagnation point. This model has been installed in the RPI 24-in. diameter Hypersonic Shock Tunnel and used to test the Directed-Energy Air Spike concept. Pitot pressures have been measured at the maximum diameter annular region of the blunt body. Surface pressure and pitot rake pressure surveys as well as the Schlieren photographs will be presented for Mach number 10 with 15-25 kW power at the tip of the spike
Keywords: Directed-Energy Air Spike (DEAS), Hypersonic Flows, Hypersonic vehicle
COB693 NUMERICAL SIMULATION OF TWO-DIMENSIONAL BOUNDARY LAYER SEPARATION CONTROL / SIMULAÇÃO NUMÉRICA DO CONTROLE DA SEPARAÇÃO DE UMA CAMADA LIMITE BIDIMENSIONAL
Norberto Mangiavacchi, Gregory Hernandez, Thilo Schoenfeld, Franck Nicoud
CERFACS, 42 avenue Gustave Coriolis, F-31057 Toulouse, France
* Currently at NACAD-COPPE/UFRJ, Caixa Postal 68516, CEP 21945-970, Rio de Janeiro, RJ, Brazil. E-mail: norberto@coc.ufrj.br
The control of the separation on two-dimensional boundary layers at low Mach numbers is analyzed by time-accurate numerical solutions of the compressible Navier-Stokes equations. The control strategy is based on the application of a variable suction/blowing in the proximity of the separation. Open-loop unsteady suction/blowing actuations show the sensitivity of the flow to the control strategy. A simple closed-loop proportional control has been implemented, that uses a tangential shear stress sensor for the feedback control, and that controls the normal velocity at the actuator position. Parallel numerical simulations were performed with the AVBP library on a 32-processor Meiko CS-2, and on a 4-processor IBM SP2. Results show the effectiveness of the control approach in stabilizing the flow and suppressing
the periodic shedding of vortices.
Keywords: Active control, boundary layer separation, numerical simulation./ Controle ativo, separação de camada limite, simulação numérica.
COB716 OBTENÇÃO DE MODELO DE PERDAS DE PRESSÃO TOTAL EM COMPRESSORES AXIAIS / MODELLING OF TOTAL PRESSURE LOSS IN AXIALS COMPRESSORS
Júlio Santana Antunes1 , Maria de Fátima Castro Lacaz Santos1, João Luiz Filgueiras Azevedo2, João Roberto Barbosa2 e Edson Basso2
1Departamento de Matemática - Faculdade de Engenharia - UNESP - Guaratinguetá
CEP 12500-000 Guaratinguetá, Brasil - E-mail: santana@feg.unesp.br.
2IAE-ASE - Centro Tecnológico de Aeronáutica - São José dos Campos
CEP 12228-900 São José dos Campos, Brasil - E-mail: azevedo@ase2.cta.br.
The paper presents simulations of cascade flows using the two-dimensional Navier-Stokes equations. An implicit, approximate factorization method which allows the simulation of flows regardless of the speed regime is adopted. Spatial discretization of the governing equations uses a central difference algorithm. Boundary conditions are implemented based on one-dimensional characteristic relations for the Euler equations. Numerical tests are performed for flows in axial compressors with DCA profiles.
Keywords: Navier-Stokes, Compressores Axiais, Simulação Numérica, Escoamento Compressível, Diferenças Finitas Navier-Stokes, Axials Compressors, Numerical Simulation, Compressivel Flow, Finites Differences
COB1227 ESTUDO ANALÍTICO DOS FENÔMENOS TRANSITÓRIOS OCASIONADOS POR GRANDES BOLSAS DE AR CONFINADAS NOS SISTEMAS HIDRÁULICOS
Carlos Augusto de Carvalho Magalhães, Rodrigo de Melo Porto & Hans George Arens
Departamento de Hidráulica e Saneamento, Escola de Engenharia de São Carlos - EESC - USP
CEP: 13.560-250 - Caixa Postal 539 - São Carlos, Brasil - E-mail: cacmagal@sc.usp.br
The flow in a hydraulic installation can be affected by various conditions such as starting or stopping the pumps or turbines and the changes in the valve setting. During such conditions, there arise situations in wich pressures and velocities in pipes can be determined by mathematical models in order to verify if their extreme values are within the admissible range. One of the reasons for the transient behavior is the presence of air confined during these alterations. When the pipes are not properly designed or if it is not completely full or air bleeding, large amounts of air may be confined in the system. Pockets of air can cause severe transient behavior if such pockets deslocate from one place to the other giving rise to local acceleration and consequently large velocities and pressures. The higher pressure may be of the order of 15 times the static pressure in the system. Thus, this paper considers pratical and safe procedure (rigid or elastic models) that permit calculation of transient pressures given that there is no analytical solution available. This study also conducts a sensitivity analysis on the various factors involved in the problem.
Keywords: air pockets; hydraulic transients; waterhammer; bolsas de ar; transientes hidráulicos.
COB1406 - THE GENERATION OF NONLINEAR WAVES BY A PISTON-TYPE WAVE MAKER
JULIO TOMAS AQUIJE CHACALTANA y & ANTONIO FERNANDO TELES DA SILVA
y Dpto. Mecânica Computacional, CNPq/ Laboratorio Nacional de Computação Científica
CEP 22220--160 R. Lauro Müller, 455, RJ.--Brazil: juliotac@alpha.lncc.br
Lab. Mec. Fluidos, PEM/Coppe/ UFRJ & Inst. de Matemática/UFRJ,
CP 68503 CEP 21945--970, Rio de Janeiro, RJ.--Brazil: fernando@labmf1.com.ufrj.br
Abstract
The generation of large amplitude waves by a wave-maker in a canal is simulated with a Boundary In-
tegral numerical code. The code is based on Potential Theory and the free surface boundary conditions,
dynamical and kinematical are taken as completely nonlinear. Results allow for assessments of experi-
mental and theoretical work. Short and long waves are generated according to the analytic motions, for
the wave-maker, derived in the classic work of Ursell, Dean and Yu 1959, based on linear approximations.
Keywords
Piston-type Wave-maker, Nonlinear Boundary Conditions, Wave generation.
COB1405 - MODELAGEM DA TECTONICA DE PLACAS NA CROSTA TERRESTRE
/ MODELLING OF PLATE TECTONICS ON EARTH'S CRUST
ROGER MATSUMOTO MOREIRA y & ANTONIO FERNANDO TELES DA SILVA
y Departamento de Desenho Técnico, Escola de Engenharia, CTC/UFF
R.Paço da Pátria,156,bl.D,sl.505 CEP24210-240 RJ Brasil -- E-mail: roger@labmf1.com.ufrj.br
z Laborat'orio de Mec"anica dos Fluidos, PEM/COPPE/UFRJ & Instituto de Matem'atica/UFRJ
CP68503 CEP21945-970 RJ Brasil -- E-mail: fernando@labmf1.com.ufrj.br
Abstract
A simplified modelling of the interaction between the continental lithosphere and the asthenosphere
underneath it is proposed; in this model the lithosphere is considered as a rigid slab moving over and onto
a viscous layer, that represents the asthenosphere. The asthenosphere, laying underneath the lithosphere,
is represented as a fluid of very high viscosity; also the thinner lithospheric layer forming the ocean floor
layer has been supressed, leaving in its place a free surface. The transient Stokes flow resulting from the
translation of the rigid slab is modelled and solved by a Boundary Integral equation based on Lorentz
reciprocal theorem.
Keywords
Movimento de placas tectônicas / Plate tectonics, escoamento de Stokes / Stokes flow, M'etodo da Integral
de Contorno / Boundary Integral Method.