Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
47
4
2020
NUMERICAL PREDICTION OF FLOW THROUGH A P4119 PROPELLER USING A HYBRID MESH TECHNIQUE
291-307
10.1615/InterJFluidMechRes.2020029116
N.
Prakash
Department of Automobile Engineering, Hindustan Institute of Technology and Science,
Chennai, 603103, Tamil Nadu, India
D. G.
Roychowdhury
Hindustan Institute of Technology and Science, Chennai, India
A.
Muthuvel
Department of Mechanical Engineering, Sai Ram College of Engineering, Hosur, India
Abd Elnaby
Kabeel
Mechanical Power Engineering Department, Faculty of Engineering, Mechanical Power
Engineering Department, Tanta University, Egypt
Prasad
Chandran
Department of Automobile Engineering, Hindustan Institute of Technology and Science,
Chennai, India
Ali J.
Chamkha
Mechanical Engineering Department, Prince Sultan Endowment for Energy and
Environment, Prince Mohammad Bin Fahd University, Al-Khobar 31952, Saudi Arabia; RAK Research and Innovation Center, American University of Ras Al Khaimah, P.O. Box
10021, Ras Al Khaimah, United Arab Emirates
Ravishankar
Sathyamurthy
KPR Institute of Engineering and Technology
CFD
propeller
hydrodynamic coefficients
moving reference frame
interface
turbulent
laminar
tip vortex
A three-dimensional steady-state analysis of a three-bladed DTMB P4119 propeller is carried out with a hybrid mesh using the k-ε V2F turbulence model, and assuming the flow past the propeller to be laminar. The simulation is carried out for various advance ratios: J = 0.5, 0.833, 0.889, and 1.1. The predicted hydrodynamic coefficients, such as the thrust coefficient (Kt), torque coefficient (Kq), and coefficient of pressure (Cp), compare very well with experimental results for both the design as well as off-design advance ratios. Also, for the design advance ratio, both models predict the circumferentially averaged axial, radial, and tangential velocities very well. It is observed that the majority of the flow over the blade surface is laminar, and both the k-ε V2F and laminar models can capture the tip vortex very well. Hence, both models can be used to predict the hydrodynamic parameters effectively.
VORTEX IDENTIFICATION AND PROPER ORTHOGONAL DECOMPOSITION OF RIGID FLAPPING WING
309-328
10.1615/InterJFluidMechRes.2020025629
Srikanth
Goli
Aerospace Engineering, Indian Institute of Technology, Kharagpur, 721302, India
Sai Sandeep
Dammati
Aerospace Engineering, Indian Institute of Technology, Kharagpur, 721302, India
Arnab
Roy
Aerospace Engineering, Indian Institute of Technology, Kharagpur, 721302, India
Subhransu
Roy
Mechanical Engineering, Indian Institute of Technology, Kharagpur, 721302, India
flapping motion
vortex identification
proper orthogonal decomposition
The present study is focused on vortex identification and proper orthogonal decomposition (POD) of the flow field generated by a rigid wing in main flapping motion. Experiments are conducted for a rigid rectangular wing of aspect ratio (AR) 1.5 at two different flapping frequencies f = 1.5 and 2 Hz with water as the fluid medium. The main flapping mechanism executes asymmetric lower-upper stroke of 1:3 ratio single degree of freedom motion. Two-dimensional particle image velocimetry (PIV) measurement technique has been used to generate the velocity field at each discrete flapping angle by illuminating the mid chord plane of the wing. Three different Galilean invariant methods, namely λ2 criterion, Q criterion, and Δ criterion, have been used for vortex identification. Limited comparison has been made with a new omega method. These methods were found to be consistent in detecting swirling vortices or coherent structures (CS). Proper orthogonal decomposition was used to exhibit the most energetic modes of the flow field. The captured modes were identified to be in-connect with vortex identification methods. The combination of these tools was more effective in comparison with velocity field data for achieving a deeper understanding of the complex flow produced by the flapping wing.
TOWARD OPTIMAL WAVY SURFACE SHAPE FOR HIGH-SPEED BOUNDARY LAYER STABILIZATION
329-335
10.1615/InterJFluidMechRes.2020033001
Alexander Vitalyevich
Fedorov
Central Aerohydrodynamic Institute (TsAGI), 1, Zhukovsky Str., Zhukovsky,
Moscow Region, 140180, Russian Federation; Moscow Institute of Physics and Technology (MIPT), 9 Institutskiy Per.,
Dolgoprudny, Moscow Region, 141701, Russian Federation
Andrey V.
Novikov
Central Aerohydrodynamic Institute, Zhukovsky, 140180, Russia; Moscow Institute of Physics and Technology (National Research University), Dolgoprudny,
141701, Russia
Nikolai N.
Semenov
Moscow Institute of Physics and Technology (National Research University), Dolgoprudny,
141701, Russia
laminar flow control
wavy wall
high-speed boundary layer
numerical simulation
Aerodynamic parameters and stability of a near-wall flow over wavy plates of varying shapes in the free stream of Mach = 6 are investigated by means of numerical simulations. The wavy wall produces a stabilizing effect on a highspeed boundary layer by reducing second-mode instability amplitudes that may eventually delay the laminar-turbulent transition onset. However, the wavyness changes an aerodynamic drag of the surface. In this work a dependency of the stabilizing effect and aerodynamic parameters on the wavy wall shape are investigated. The simulations are done by integrating Navier-Stokes equations using an in-house HSFlow solver, which implements an implicit finite-volume shock-capturing method with the second-order approximation in space and time. Second-mode instabilities are excited by a high-frequency actuator of suction-blowing type placed on the wall. It is shown that with an increasing number of cavities the stabilizing effect is enhanced while the total aerodynamic drag coefficient reaches a certain level. This study helps to clarify robustness of the wavy wall stabilization concept at high speeds.
EXPERIMENTAL AND NUMERICAL INVESTIGATION OF SUDDENLY EXPANDED FLOW FIELD FOR SUPERSONIC MACH NUMBERS WITH AND WITHOUT ANNULAR CAVITIES
337-356
10.1615/InterJFluidMechRes.2020032551
Jaimon Dennis
Quadros
Department of Mechanical Engineering, Birla Institute of Technology, Ras-Al-Khaimah,
United Arab Emirates
S. A.
Khan
Department of Mechanical Engineering, International Islamic University Malaysia, Kuala
Lampur, Malaysia
T.
Prashanth
Department of Mechanical Engineering, Global Academy of Technology, Bangalore, India
cavities
nozzle
base pressure
wall pressure
Mach number
nozzle pressure ratio
area ratio
length to diameter ratio (L/D)
The influence of cavities on a suddenly expanded flow field was analyzed. Air flow was passed through a convergent divergent axisymmetric nozzle, and expanded suddenly into a circular parallel shroud with annular cavities. Base pressure and wall pressures were measured for combinations of process variables, such as Mach number (M), nozzle pressure ratio (NPR), area ratio (AR), the length to diameter ratio (L/D) of the enlargement section, and the cavity aspect ratio. The experimental results showed that the base pressure fin the suddenly expanded flow field was significantly influenced by annular cavities for low area ratios and high nozzle pressure ratios. The cavities also yielded a weaker vortex street in the near wake in the vicinity of the nozzle exit, causing a slight increase in the base pressure for low Mach numbers. The wall pressure studies showed that the introduction of cavities generated secondary vortices which reduced the oscillatory nature of the flow along the duct length. The generation of secondary vortices was confirmed by a numerical analysis of the suddenly expanded flow field without and with annular cavities. The two-dimensional coupled implicit Reynolds Averaged Navier-Stokes equations and the two equation standard k-ε turbulence model simulated the process numerically. The governing equations (continuity, momentum, and energy), along with the boundary conditions, were solved by the finite element method. They were flow patterns for various combinations of the process variables demonstrated that there is formation of secondary vortices for flows with annular cavities. Due to the formation of near wake and free shear instability, the vortices of these flows caused the boundary layer to roll up, forming secondary vortices in the suddenly expanded flow field. Immediately following their formation, the vortices underwent a strong three-dimensional distortion.
THERMOPHORESIS AND BROWNIAN MOTION EFFECTS ON NATURAL CONVECTION HEAT AND MASS TRANSFER OF FRACTIONAL OLDROYD-B NANOFLUID
357-370
10.1615/InterJFluidMechRes.2020030598
Jinhu
Zhao
School of Mathematics and Statistics, Fuyang Normal University, Anhui, China
fractional Oldroyd-B model
heat and mass transfer
nanofluid
Brownian motion
thermophoresis effect
We investigated the effects of Brownian motion and thermophoresis on unsteady convection heat and mass transport of nanofluid, where the fractional Oldroyd-B model is employed in the constitutive relation. The nonlinear boundary layer governing equations not only have multi-term time fractional derivatives, but also possess special mixed time space operators in the convection velocity term. Numerical solutions were obtained by finite difference method combined with L1-algorithm. The effects of fractional derivative parameters (α, 0 ~ 0.5; β, 0.2 ~ 1), Brownian motion number (Nb, 0.3 ~ 0.9), and thermophoresis number (Nt, 0.1 ~ 0.9) are discussed in detail. Results indicate that thermophoresis and Brownian motion had a strong influence on the heat and mass transfer of nanofluid. With an increased thermophoresis number, the temperature profiles rose significantly, while the enhancement of Brownian motion led to the decline of the concentration. The intersection points of the velocity profiles demonstrate that the fractional viscoelastic nanofluid had a relaxation response in the velocity transport process.
NUMERICAL SIMULATION STUDY ON BIONIC MUCUS DRAG REDUCTION OF UNDERWATER VEHICLE
371-385
10.1615/InterJFluidMechRes.2020034583
Kaisheng
Zhang
Department of Mechatronics Engineering, College of Engineering, Ocean
University of China, Qingdao, China
Chaofan
Ma
Department of Mechatronics Engineering, College of Engineering, Ocean University of China,
Qingdao, China
Baocheng
Zhang
Department of Mechatronics Engineering, College of Engineering, Ocean
University of China, Qingdao, China
Bo
Zhao
Department of Mechatronics Engineering, College of Engineering, Ocean University of China,
Qingdao, China
Qiang
Wang
Department of Mechatronics Engineering, College of Engineering, Ocean University of China,
Qingdao, China
underwater vehicle
bionic mucus drag reduction
viscoelastic fluid
numerical simulation
The surface characteristics of fish have excellent drag reduction capabilities. Compared with scales, the mucus secreted by the fish body surface has even better results. In this paper, the FENE-P constitutive model and the mixture multiphase flow model are used to simulate the drag reduction effect of the underwater vehicle secreting mucus (viscoelastic fluid) to form a mucous membrane on the outer surface from the perspective of bionics. The simulation results show that the drag reduction rate of the mucous membrane can reach about 17%. The increase in the thickness of the boundary layer caused by the mucus and the backward movement of the separation point are the main reasons for the decrease in resistance. The turbulence statistics of the boundary layer of the aircraft and the Reynolds stress are also compared, and the influence of the parameter change on the drag coefficient is obtained. The maximum drag reduction rate occurs when the viscosity ratio is 0.8, the maximum molecular stretch length is 80, and the Weissenberg number is 20, which provides a new method for drag reduction of underwater vehicles.