Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
40
1
2013
Experimental Investigation of the Interaction between Turbulent Impinging Flame and Radiation
1-8
Nadjib
Ghiti
Laboratoire de Mécanique Avancée − LMA Bab-Ezzouar, Alger, Algeria
Abed Alhalim
Bentebbiche
Laboratoire de Mécanique Avancée − LMA Bab-Ezzouar, Alger, Algeria
Ramzi
Boulkroune
URASM-CSC, Unité de recherche Appliquèe en Sidérurgie Métallurgie − Centre National de Recherche Scientifique et Technique en Soudage et Contrôl Annaba, Algeria
An experimental study was focused on the investigation of the interaction between turbulent and radiation in the case of a methane turbulent impinging diffusion
flame. An infrared thermograpgy was used to measure the flame radiation temperature based on a fixed emissivity. Then the flame radiation heat flux was calculated for two Reynolds numbers 4500, 6000 and for tow distances L/d from the wall to the center line of the jet axis. The results show that the flame radiation heat flux is more influenced by the increasing of the Reynolds number and with the decreasing of the distance between the flame and the lateral wall.
On Blood Flow in an Artery with an Unsteady Overlapping Stenosis: Mathematical and Computer Modeling
9-26
Ranadhir
Roy
School of Mathematical and Statistical Sciences,
One West University Boulevard, University of Texas Rio Grande Valley, Brownsville, Texas 78520 USA
Daniel N.
Riahi
School of Mathematical and Statistical Sciences,
One West University Boulevard, University of Texas Rio Grande Valley, Brownsville, Texas 78520 USA
In this study, we investigate the characteristics of blood flow in an artery with an overlapping unsteady stenosis. Due to the unsteadiness of the stenosis and its boundary effect on the blood flow system, the resulting flow is assumed to be unsteady with the same frequency as the one generated by the unsteady stenosis. The governing equations for the mass conservation and momentum are used for blood flow system, but here the dynamic viscosity of the fluid is a function of the radial variable as modeled by Einstein to take into account the hematocrit. Hematocrit is the percentage of the red cells by volume in the whole blood fluid. Mathematical models and computational codes are developed to determine the leading order flow velocity, pressure gradient, impedance and wall shear stress at the throats and at the critical height of the stenosis. We find that higher values of the frequency, hematocrit, and height of stenosis leads to higher values of the axial velocity, the impedance and the wall shear stress in the stenosis zone.
Numerical Studies on Air-Core Vortex Formation During Draining of Liquids from Tanks
27-41
Prateep
Basu
Dept. of Aerospace Engineering, Indian Institute of Space Science and Technology, Trivandrum, India
Dheeraj
Agarwal
Dept. of Aerospace Engineering, Indian Institute of Space Science and Technology, Trivandrum, India
T. John
Tharakan
Liquid Propulsions Systems Centre, Indian Space Research Organization,Valiamala, Thiruvananthapuram 695547, India
Abdusamad
Salih
Department of Aerospace Engineering
Indian Institute of Space Science and Technology
Thiruvananthapuram - 695547, India
The gas-liquid interface dips during the draining of a liquid through a discharge port of a vessel or a tank. The dip develops into a gas-core vortex which subsequently enters the discharge port. This entry can be either gradual or sudden, depending on the intensification of the rotational flow currents during the draining process. The extension of the gas-core into the drain port reduces the
flow area and consequently the flow rate. In liquid propellant rocket motors, this phenomenon can have adverse effect on the performance as well as lead to under
utilisation of the propellant. In this paper, the authors have tried to find the reason why such an air-core vortex develops in the first place, and the factors that influence its intensification over time, as reported in literature. These investigations have been carried out through simulations done using the commercial
ANSYS Fluent code to validate the findings from the CFD results. The simulations are carried out using the volume of fluid (VOF) method, which obtains the volume fraction of each of the fluid throughout the domain and thereby captures the gas-liquid interface motion. Thereafter, the air-core vortex height predictions are validated with results reported in the literature.
A Study of Wake Vortex in the Scour Region around a Circular Pier
42-59
Subhasish
Das
School of Water Resources Engineering, Jadavpur University, Kolkata, West Bengal, India
Ranajit
Midya
School of Water Resources Engineering, Jadavpur University Kolkata, West Bengal, India
Rajib
Das
School of Water Resources Engineering, Jadavpur University, Kolkata 700032, India
Asis
Mazumdar
School of Water Resources Engineering, Jadavpur University, Kolkata 700032, India
Wake vortex scour is very important when successive piers (one downstream of other) are kept. In case of successive pier arrangement, the wake vortex of the upstream pier may influence the horseshoe vortex of the pier placed downstream. If the piers are arranged eccentrically then the sediment movement may take place towards the side wall of the flume as well as along the downstream.
For this reason the study of turbulent flow characteristics of a wake vortex within an equilibrium scour hole is very important. In the present paper the outcome of experimental study on the turbulent wake vortex flow at cylindrical pier measured by an acoustic Doppler velocimeter (ADV) were presented. In this study three
different piers were used with diameters 0.10 m, 0.075 m and 0.05 m. Vector plots of the flow field reveal the vorticity and circulation characteristics of the
wake vortex flow associated with an upflow at equilibrium scour hole condition. Results show that the non dimensional wake vortex circulation increases at y = 0 and ±3 until Rep value reaches around 2.40·104 but then it decreases with further increase in Rep, as the wake vortices are washed away due to further increase of inertia force. Similar trend was observed when the non-dimensional circulation was presented with respect to different pier diameter as well as at different nondimensional inflow depth. The non-dimensional circulation along the centreline (y = 0) of the flume is lesser than y = ±3 which verifies that the wake vortices get weaker when they come closer to the centreline of flow.
On the Use of Laser Tomography Techniques for Validating CFD Simulations of the Flow in Supersonic Ejectors
60-70
Philippe
Desevaux
Institut FEMTO-ST-UMR 6174, Département Energie, Université de Franche-Comté, Parc Technologique, Belfort, France
A.
Bouhanguel
Institut FEMTO-ST-UMR 6174, Département Energie, Université de Franche-Comté, Parc Technologique, Belfort, France
L.
Girardot
Institut FEMTO-ST-UMR 6174, Département Energie, Université de Franche-Comté, Parc Technologique, Belfort, France
E.
Gavignet
Institut FEMTO-ST-UMR 6174, Département Energie, Université de Franche-Comté, Parc Technologique, Belfort, France
This paper reviews some possibilities offered by several flow visualization methods to validate numerical simulations of the flow in supersonic air ejectors.
The visualizations techniques are all based on the laser sheet method but differ from each other by the kind of the illumination source, the polarization direction
of the incident light and the type of the scattering tracers. Each of these methods enables the visualization of specific flow phenomena (shock structure, condensation and mixing processes, flow instabilities). The experimental flow visualizations obtained using these methods are compared with numerical flow visualizations and are proven very effective to help in the validation of CFD simulations.
Unconfined Flow and Heat Transfer around a Square Cylinder at Low Reynolds and Hartmann Numbers
71-90
Dipankar
Chatterjee
Academy of Scientific and Innovative Research (AcSIR), CSIR-Central Mechanical
Engineering Research Institute, Durgapur-713209, India; Advanced Design and Analysis Group, CSIR-Central Mechanical Engineering Research
Institute Durgapur-713209, India
Kanchan
Chatterjee
Department of Mechanical Engineering, Dr. B. C. Roy Engineering College, Durgapur, India
The forced convection heat transfer is analyzed through a two-dimensional numerical simulation following a finite volume approach for the hydromagnetic flow around a square cylinder at low Reynolds numbers. The cylinder is placed
in an unconfined medium and acted upon by the magnetohydrodynamic (MHD) flow of a viscous incompressible and electrically conductive fluid. The magnetic
field is applied either along the streamwise or transverse directions. Fictitious confining boundaries are considered on the lateral sides of the simulation domain to make the problem computationally feasible. The simulation is carried out for the range of Reynolds number 10 ≤ Re ≤ 50 with Hartmann number 0 ≤ Ha ≤ 10 and with a fixed Prandtl number, Pr = 0.02 (liquid metal) and a blockage parameter, β = d/H = 5%. The flow is steady and stable for the above range of conditions. The magnetic field provides additional stability to the flow as a result of which the wake region behind the cylinder reduces with increasing magnetic field strength at any Reynolds number. The critical magnetic field strength is also computed for which the separation is completely suppressed for the Reynolds number range in case of transversely applied magnetic field. The rate of heat transfer is found almost invariant at low Reynolds number whereas it increases
slightly for higher Reynolds number with the applied magnetic field. The heat transfer increases as usual with the Reynolds number for all Hartmann numbers.