scholarly journals Numerical Contribution to Airflow Study Through a Generic Merchant Ship Models

2020 ◽  
Vol 15 ◽  
Keyword(s):  
Wind Tunnel ◽  
Numerical Study ◽  
Three Dimensional ◽  
Numerical Results ◽  
Numerical Code ◽  
Generic Models ◽  
Merchant Ship ◽  
Acceleration And Deceleration ◽  
Low Speed Wind Tunnel ◽  
Good Agreement

The merchant ships are continuously recruited by the world meteorological organization (WMO) as Voluntary Observing Ship (VOS) for the collect of meteorological parameters at the ocean surface. VOS meteorological observation includes many parameters such as the wind speed measured by anemometers. This measurement is biased by the presence of ship and superstructure. Little work was carried out in this field. Between them we find the experimental work at a low speed wind tunnel of Southampton University which studies the airflow distortion over simple models (generic models) of VOS merchant ship. This study presents numerical results of a 3D simulation analyzing airflow effect above the bridge of a generic merchant ship models involved in VOS. For this purpose three-dimensional, stationary and turbulent, numerical simulation has been achieved the flow over the bridge of a tanker and a container ship at 1/ 46 scale using a numerical code and CFX code with turbulence k-ε models. This numerical study allows us to know the position of the line of equality as well as the zone of acceleration and deceleration of the flow. The results obtained numerically by numerical code and CFX code are compared with those obtained experimentally in the wind tunnel of Southampton University. Numerical results are in a good agreement with experimental results and can be used as a reference to find the position of the equality line and to know the error range in of the anemometer velocity reading.

Numerical Study of the Injection Process in a Transonic Wind Tunnel—Part I: The Design Point

2006 ◽  
Vol 129 (6) ◽  
pp. 682-694 ◽  
Author(s):  
João B. P. Falcão Filho ◽  
Marcos A. Ortega
Keyword(s):  
Wind Tunnel ◽  
Numerical Study ◽  
Research Effort ◽  
Three Dimensional ◽  
Numerical Code ◽  
Navier Stokes ◽  
Main Stream ◽  
Design Point ◽  
Injection Process ◽  
Transonic Wind Tunnel

Injectors are to be installed in a transonic wind tunnel with the ultimate objective of expanding the Reynolds number envelope. The aim of this research effort is to numerically simulate the steady mixing process involving the supersonic jets and the tunnel subsonic main stream. A three-dimensional, Reynolds-averaged Navier–Stokes numerical code was developed following the main lines of the finite-difference diagonal algorithm, and turbulence effects are accounted for through the use of the Spalart and Allmaras one-equation scheme. This paper focuses on the “design point” of the tunnel, which establishes (among other specifications) that the static pressures of both streams at the entrance of the injection chamber are equal. Three points are worth noting. The first is related to the numerical strategy that was introduced in order to mimic the real physical process in the entire circuit of the tunnel. The second corresponds to the solution per se of the three-dimensional mixing between several supersonic streams and the subsonic main flow. The third is the calculation of the “engineering” parameters, that is, the injection loss factor, gain, and efficiency. Many interesting physical aspects are discussed, and among them, the formation of three-dimensional shocks’ and expansions’ “domes”

Numerical Study on Supersonic Combustor with an Allotype Cavity

2014 ◽  
Vol 694 ◽  
pp. 187-192
Author(s):  
Jin Xiang Wu ◽  
Jian Sun ◽  
Xiang Gou ◽  
Lian Sheng Liu
Keyword(s):  
Alternative Model ◽  
Numerical Study ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Experimental Result ◽  
Navier Stokes ◽  
Cold Flow ◽  
Hypersonic Inlet ◽  
Good Agreement

The three-dimensional coupled explicit Reynolds Averaged Navier–Stokes (RANS) equations and the two equation shear-stress transport k-w (SST k-w) model has been employed to numerically simulate the cold flow field in a special-shaped cavity-based supersonic combustor. In a cross-section shaped rectangular, hypersonic inlet with airflow at Mach 2.0 chamber, shock structures and flow characteristics of a herringbone-shaped boss and a herringbone-shaped cavity models were discussed, respectively. The results indicate: Firstly, according to the similarities of bevel-cutting shock characteristics between the boss case and the cavity case, the boss structure can serve as an ideal alternative model for shear-layer. Secondly, the eddies within cavity are composed of herringbone-spanwise vortexes, columnar vortices in the front and main-spanwise vortexes in the rear, featuring tilting, twisting and stretching. Thirdly, the simulated bottom-flow of cavity is in good agreement with experimental result, while the reverse flow-entrainment resulting from herringbone geometry and pressure gradient. However, the herringbone-shaped cavity has a better performance in fuel-mixing.

Numerical Modeling of Near Fault Seismic Ground Motion for Denali Fault

2021 ◽  
Vol 12 (2) ◽  
pp. 0-0
Keyword(s):  
Ground Motion ◽  
Peak Ground Acceleration ◽  
Numerical Study ◽  
Ground Motions ◽  
Numerical Results ◽  
Fault Rupture ◽  
Ground Acceleration ◽  
Denali Fault ◽  
Near Fault ◽  
Good Agreement

An effective earthquake (Mw 7.9) struck Alaska on 3 November, 2002. This earthquake ruptured 340 km along Susitna Glacier, Denali and Totschunda faults in central Alaska. The peak ground acceleration (PGA) was recorded about 0.32 g at station PS10, which was located 3 km from the fault rupture. The PGA would have recorded a high value, if more instruments had been installed in the region. A numerical study has been conducted to find out the possible ground motion record that could occur at maximum horizontal slip during the Denali earthquake. The current study overcomes the limitation of number of elements to model the Denali fault. These numerical results are compared with observed ground motions. It is observed that the ground motions obtained through numerical analysis are in good agreement with observed ground motions. From numerical results, it is observed that the possible expected PGA is 0.62 g at maximum horizontal slip of Denali fault.

scholarly journals Experimental and Numerical Study on Dynamics of Two Footbridges with Different Shapes of Girders

2020 ◽  
Vol 10 (13) ◽  
pp. 4505 ◽  
Author(s):  
Anna Banas ◽  
Robert Jankowski
Keyword(s):  
Natural Vibration ◽  
Numerical Study ◽  
Numerical Results ◽  
Vibration Exciter ◽  
Structural Vibrations ◽  
Impulse Load ◽  
Different Shapes ◽  
Comfort Criteria ◽  
Good Agreement

The paper presents the experimental and numerical results of the dynamic system identification and verification of the behavior of two footbridges in Poland. The experimental part of the study involved vibration testing under different scenarios of human-induced load, impulse load, and excitations induced by vibration exciter. Based on the results obtained, the identification of dynamic parameters of the footbridges was performed using the peak-picking method. With the impulse load applied to both structures, determination of their natural vibration frequencies was possible. Then, based on the design drawings, detailed finite element method (FEM) models were developed, and the numerical analyses were carried out. The comparison between experimental and numerical results obtained from the modal analysis showed a good agreement. The results also indicated that both structures under investigation have the first natural bending frequency of the deck in the range of human-induced excitation. Therefore, the risk of excessive structural vibrations caused by pedestrian loading was then analysed for both structures. The vibration comfort criteria for both footbridges were checked according to Sétra guidelines. In the case of the first footbridge, the results showed that the comfort criteria are fulfilled, regardless of the type of load. For the second footbridge, it was emphasized that the structure meets the assumptions of the guidelines for vibration severability in normal use; nevertheless, it is susceptible to excitations induced by synchronized users, even in the case of a small group of pedestrians.

scholarly journals On the aerodynamic flow around a cyclist model at the hoods position

2019 ◽  
Vol 23 (1) ◽  
pp. 35-47 ◽  
Author(s):  
Jiun-Jih Miau ◽  
Shang-Ru Li ◽  
Zong-Xiu Tsai ◽  
Mai Van Phung ◽  
San-Yi Lin
Keyword(s):  
Wind Tunnel ◽  
Water Channel ◽  
Three Dimensional ◽  
Simulation Method ◽  
Reynolds Numbers ◽  
Numerical Results ◽  
Wake Flow ◽  
Model Surface ◽  
Eddy Simulation ◽  
Separation Pattern

Abstract Aerodynamic flow around an 1/5 scale cyclist model was studied experimentally and numerically. First, measurements of drag force were performed for the model in a low-speed wind tunnel at Reynolds numbers from $$5.5 \times 10^{4}$$5.5×104 to $$1.8 \times 10^{5}$$1.8×105. Meanwhile, numerical computation using a large eddy simulation method was performed at three Reynolds numbers of $$1.1 \times 10^{4}$$1.1×104, $$6.5 \times 10^{4}$$6.5×104 and $$1.5 \times 10^{5}$$1.5×105 to obtain the drag coefficients for comparison. Second, flow visualization was made in a water channel and the wind tunnel mentioned to examine the three-dimensional flow separation pattern on the model surface, which could also be realized from the numerical results. Finally, a wake flow survey based on the hot-wire measurements in the wind tunnel showed that in the near-wake region, the flow was featured with the formation of multiple streamwise vortices. The numerical results further indicated that these vortices were evolved from the separated flows occurred on the model surface. Graphic Abstract

PREDICTION OF UNSTEADY STATES IN LID-DRIVEN CAVITIES FILLED WITH AN INCOMPRESSIBLE VISCOUS FLUID

2012 ◽  
Vol 23 (04) ◽  
pp. 1250030 ◽  
Author(s):  
FAYÇAL HAMMAMI ◽  
NADER BEN-CHEIKH ◽  
ANTONIO CAMPO ◽  
BRAHIM BEN-BEYA ◽  
TAIEB LILI
Keyword(s):  
Reynolds Number ◽  
Numerical Study ◽  
Three Dimensional ◽  
Staggered Grid ◽  
Three Dimensional Flow ◽  
Driven Cavity ◽  
Flow Evolution ◽  
2D And 3D ◽  
Benchmark Solutions ◽  
Good Agreement

In this work, a numerical study devoted to the two-dimensional and three-dimensional flow of a viscous, incompressible fluid inside a lid-driven cavity is undertaking. All transport equations are solved using the finite volume formulation on a staggered grid system and multi-grid acceleration. Quantitative aspects of two and three-dimensional flows in a lid-driven cavity for Reynolds number Re = 1000 show good agreement with benchmark results. An analysis of the flow evolution demonstrates that, with increments in Re beyond a certain critical value Rec, the steady flow becomes unstable and bifurcates into unsteady flow. It is observed that the transition from steadiness to unsteadiness follows the classical Hopf bifurcation. The time-dependent velocity distribution is studied in detail and the critical Reynolds number is localized for both 2D and 3D cases. Benchmark solutions for 2D and 3D lid-driven cavity flows are performed for Re = 1500 and 6000.

Fluid Flow and Lateral Fluid Dispersion in Bounded Granular Beds

2002 ◽  
Author(s):  
Azita Soleymani ◽  
Eveliina Takasuo ◽  
Piroz Zamankhan ◽  
William Polashenski
Keyword(s):  
Reynolds Number ◽  
Porous Media ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Numerical Study ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Numerical Results ◽  
Transition To Turbulence ◽  
Wide Range

Results are presented from a numerical study examining the flow of a viscous, incompressible fluid through random packing of nonoverlapping spheres at moderate Reynolds numbers (based on pore permeability and interstitial fluid velocity), spanning a wide range of flow conditions for porous media. By using a laminar model including inertial terms and assuming rough walls, numerical solutions of the Navier-Stokes equations in three-dimensional porous packed beds resulted in dimensionless pressure drops in excellent agreement with those reported in a previous study (Fand et al., 1987). This observation suggests that no transition to turbulence could occur in the range of Reynolds number studied. For flows in the Forchheimer regime, numerical results are presented of the lateral dispersivity of solute continuously injected into a three-dimensional bounded granular bed at moderate Peclet numbers. Lateral fluid dispersion coefficients are calculated by comparing the concentration profiles obtained from numerical and analytical methods. Comparing the present numerical results with data available in the literature, no evidence has been found to support the speculations by others for a transition from laminar to turbulent regimes in porous media at a critical Reynolds number.

scholarly journals Three-dimensional numerical study of thermal exchanges in different geometry sections of mini-channels using three different nanoparticles

10.30544/455 ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 103-119
Author(s):  
Kamel Chadi ◽  
Nourredine Belghar ◽  
Belhi Guerira ◽  
Aissam Messaoudi
Keyword(s):  
Reynolds Number ◽  
Volume Fraction ◽  
Numerical Study ◽  
Three Dimensional ◽  
Numerical Results ◽  
Junction Temperature ◽  
Ansys Fluent ◽  
Cooling Fluid ◽  
Mini Channels ◽  
Exchange Surface

In the present work, we have studied the thermal exchanges of different geometry sections of mini-channels of a cooler numerically. Particularly, we have chosen a mini channels cooler copper for cooling an electronic chip IGBT. In our simulation of three-dimensional (3D), we have compared the numerical results for the different forms of the proposed mini-channels and the three different types of nano-fluids by using the Cu-water, the Ag-water, and the Diamond-water with a volume fraction of 0.02%. The numerical results are obtained by choosing a Reynolds number (Re) between 100 and 900 and considering that the flow regime is stationary. The simulation was performed using commercial software, ANSYS-Fluent 15.0. The results obtained show that the increase of the exchange surface between the walls of the mini channels and the cooling fluid makes increases the heat exchange coefficient and the improvement of the maximum junction temperature of the electronic chip IGBT with the increase of the Reynolds number. The choice of nanoparticles has considerable effects on improving the heat transfer and the maximum junction temperature of the chip IGBT.

scholarly journals Numerical study on snow transport and drift formation

1993 ◽  
Vol 18 ◽  
pp. 135-141 ◽  
Author(s):  
Takahiko Uematsu
Keyword(s):  
Continuity Equation ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Density Field ◽  
Particle Movement ◽  
Snow Density ◽  
Fall Velocity ◽  
Snow Transport ◽  
Good Agreement

A three-dimensional, numerical simulation model for snow transport and drift formation is proposed in which saltation as well as suspension are considered as dynamic behavioral factors of moving snow particles. The procedure for simulation is as follows: (1) Air flow field is simulated solving the Reynolds equations and the continuity equation. (2) Using the result of the air field flow simulation, the blown-snow density field is simulated using the diffusion equations in which the fall velocity of blown snow particles is considered. In the boundary conditions, the particle movement of saltation is taken into consideration. (3) Finally, the snowdrift rate is computed based on the amount of snow particles not transported by saltation. This model was quantitatively tested for the phenomenon of snowdrift development. The computed results showed good agreement with observations.

Sign in / Sign up

Export Citation Format

Share Document