scholarly journals Improvement of a Diagnostic Urban Wind Model for Flow Fields around a Single Rectangular Obstacle in Micrometeorology Simulation

Fluids ◽  
2021 ◽  
Vol 6 (7) ◽  
pp. 254
Author(s):  
Mitsufumi Asami ◽  
Arata Kimura ◽  
Hideyuki Oka
Keyword(s):  
Field Model ◽  
Saddle Points ◽  
Flow Fields ◽  
Experimental Results ◽  
Zone Model ◽  
Prime Model ◽  
Near Wake ◽  
Initial Flow ◽  
Rectangular Obstacle ◽  
Wake Zone

In general, computational fluid dynamics (CFD) models incur high computational costs when dealing with realistic and complicated flows. In contrast, the mass-consistent flow (MASCON) field model provides a three-dimensional flow field at reasonable computational cost. Unfortunately, some weaknesses in simulating the flow of the wake zone exist because the momentum equations are not considered in the MASCON field model. In the present study, a new set of improved algebraic models to provide initial flow fields for the MASCON field model are proposed to overcome these weaknesses by considering the effect of momentum diffusion in the wake zone. Specifically, these models for the wake region are developed on the basis of the wake models used in well-recognized Gaussian plume models, ADMS-build and PRIME. The MASCON fields provided by the new set of wake zone models are evaluated against wind-tunnel experimental data on flow around a wall-mounted rectangular obstacle. Each MASCON field is compared with the experimental results, focusing on the positions of the vortex core and saddle points of the vortex formed in the near-wake zone and the vertical velocity distribution in the far-wake zone. The set of wake zone models developed in the present study better reproduce the experimental results in both the wake zones compared to the previously proposed models. In particular, the complicated recirculation flow which is formed by the union of the sidewall recirculation zone and the near-wake zone is reproduced by the present wake zone model using the PRIME model that includes the parameterization of the sidewall recirculation zones.

Dynamic stability of closed plasma configurations

1970 ◽  
Vol 4 (4) ◽  
pp. 645-665 ◽  
Author(s):  
Daniel R. Wells
Keyword(s):  
Global Stability ◽  
Dynamic Stability ◽  
Perturbation Analysis ◽  
Flow Fields ◽  
Experimental Results ◽  
Plasma Confinement ◽  
Gauge Symmetries ◽  
Mhd Stability ◽  
The Stability ◽  
Dynamical Principle

The global stability of closed plasma configurations is related to the dynamical principle of least constraint and the spacetime and gauge symmetries of the flow fields. This leads to an entirely new concept of MHD stability which is more basic than stability predictions which rely on a linearized perturbation analysis. The predictions of the theory are compared to recent experimental results obtained in studies of the stability of plasma confinement geometries. The theory predicts the violent ‘instabilities’ of these systems which are currently attributed to other mechanisms. Several pertinent details of the theory which are widely misinterpreted are discussed and clarified.

Prediction Laser Sealed Advanced Ceramic Coatings Dimensions by Using Finite Element Model and Computational Method

2011 ◽  
Vol 264-265 ◽  
pp. 1444-1449
Author(s):  
K.M. Adel ◽  
E.K. Ekhlas ◽  
S.H. Shaker
Keyword(s):  
Heat Affected Zone ◽  
Three Dimensional ◽  
Element Model ◽  
Melting Zone ◽  
Ceramic Coatings ◽  
Experimental Results ◽  
Computational Method ◽  
Zone Model ◽  
Good Prediction ◽  
Good Agreement

A three dimensional FE modeling of the laser surface modification is presented. The design capabilities of the ANSYS (11) software were employed for this purpose. The model calculates the dimensions of melting zone and heat affected zone. Model simulations are compared with experimental results that showed very good agreement. A one dimensional model in V.B language was presented too. The model based on conduction of heat in one dimension neglecting the other losses of heat. The results of VISUAL BASIC were compared with experimental results which showed a very good agreement. The two methods were compared with each other to showing which method have a good prediction compared with experimental results in calculating of fusion zone and heat affected zone "HAZ".

Simulation of Smoke Movement in a Loop Corridor under Mechanical Exhaust with Compound Model

2013 ◽  
Vol 475-476 ◽  
pp. 1459-1462
Author(s):  
Wei Shi ◽  
Fu Sheng Gao
Keyword(s):  
Field Model ◽  
Unit Area ◽  
Zone Model ◽  
Smoke Control ◽  
Smoke Movement ◽  
High Rise ◽  
Compound Model ◽  
Ceiling Height ◽  
Dynamic Simulator ◽  
Fire Dynamic Simulator

The mechanical smoke exhaust is as acknowledged as an effective smoke control manner by making use of some necessary exhaust facilities, also with more stability than natural exhaust. In this paper, the field model FDS (Fire Dynamic Simulator) with a combination of zone model CFAST (Consolidate Fire and Smoke Transport) were used to simulate the mechanical smoke exhaust in a loop corridor of the fire floor in a high-rise hotel, for the propose of evaluate fire safety of mechanical smoke exhaust. The mainly discussion was about the height of layer interface with the ceiling height changed, also with different smoke exhaust volume. The conclusions were obtained that, when two exhaust vents were set symmetrically in the loop corridor, the volume of smoke exhaust per unit area with 60m3/h according to regulations, always could ensure safety of smoke exhaust. The smoke exhausted worse within the corridor when ceiling height reduced. It was recommended that the ceiling lowest height limit should be provides in correlative regulation.

Accuracy Investigation of Active Flow Control Using Synthetic Jets

2015 ◽  
Vol 741 ◽  
pp. 475-480
Author(s):  
Na Gao ◽  
Chen Pu ◽  
Bao Chen
Keyword(s):  
Flow Control ◽  
Velocity Distribution ◽  
Active Flow Control ◽  
Flow Fields ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Experimental Results ◽  
Center Line ◽  
Mean Velocity ◽  
The Mean

2nd order implicit format is implemented in the Navier-Stokes code to deal with instantaneous item unsteady flows. Three simulations are made to testify the method on flow control. First, the external flow fields of synthetic jets are simulated, the mean velocity on the center line, the jet width and velocity distribution are compared well with experimental results. Secondly, the flow fields of synthetic jet in a crossflow are simulated, orifice slot, the mean velocity on the center line and velocity distribution are compared well with experimental results. Finally, the flow control experiments on separation of airfoil are simulated, control methods include steady suction and synthetic jets. Both methods show their ability to favorably effect the flow separation, shortening the length of separation bubble and improving the pressure levels in separation areas in different degrees.

Critical points in a turbulent near wake

1994 ◽  
Vol 275 ◽  
pp. 59-81 ◽  
Author(s):  
Y. Zhou ◽  
R. A. Antonia
Keyword(s):  
Critical Points ◽  
Phase Plane ◽  
Reynolds Shear Stress ◽  
Saddle Points ◽  
Normal Stresses ◽  
Flow Topology ◽  
Near Wake ◽  
Spanwise Vortex ◽  
Plane Technique ◽  
Insight Into

Velocity data were obtained in the turbulent wake of a circular cylinder with an orthogonal array of sixteen X-wires, eight in the (x, y)-plane and eight in the (x, z)-plane. By applying the phase-plane technique to these data, three types of critical points (where the velocity is zero and the streamline slope is indeterminate) were identified. Of these, foci and saddle points occurred most frequently, although a significant number of nodes was also found. Flow topology and properties associated with these points were obtained in each plane. Saddle-point regions associated with spanwise vortices provide the dominant contribution to the Reynolds shear stress and larger contributions to the normal stresses than focal regions. The topology was found to be in close agreement with that obtained from other methods of detecting features of the organized motion. The inter-relationship between critical points simultaneously identified in the two planes can provide some insight into the three-dimensionality of the organized motion. Foci in the (x, z)-plane correspond, with relatively high probability and almost negligible streamwise separation, to saddle points in the (x, y)-plane and are interpreted in terms of ribs aligned with the diverging separatrix between consecutive spanwise vortex rolls. Foci in the (x, z)-plane which correspond, with relatively weak probability, to foci in the (x, y)-plane seem consistent with a distortion of the vortex rolls in the (y, z)-plane.

scholarly journals An Independent-Flow-Field Model for a SDOF Nonlinear Structural System–Part II: Analysis of Complex Responses

2005 ◽  
Vol 128 (1) ◽  
pp. 23-30 ◽  
Author(s):  
Huan Lin ◽  
Solomon C. S. Yim
Keyword(s):  
Flow Field ◽  
Field Model ◽  
Periodic Wave ◽  
Experimental Results ◽  
Experimental Result ◽  
Structural System ◽  
Frequency Domains ◽  
Wave Heights ◽  
System Part ◽  
Good Agreement

Complex responses observed in an experimental, nonlinear, moored structural system subjected to nearly periodic wave excitations are examined and compared to the simulations of a newly proposed independent-flow-field (IFF) model in this paper. Variations in wave heights are approximated by additive random perturbations to the dominant periodic component. Simulations show good agreement with the experimental results in both time and frequency domains. Noise effects on the experimental results, including bridging and transition phenomena, are investigated and interpreted by comparing to the simulations of its deterministic counterpart. Possible causes of a chaoticlike experimental result as previously observed are also inferred.

Simulation and Analyzing of Mechanical Smoke Exhaust in a High-Rise Building

2013 ◽  
Vol 726-731 ◽  
pp. 3596-3599
Author(s):  
Wei Shi ◽  
Fu Sheng Gao
Keyword(s):  
Fire Safety ◽  
Field Model ◽  
Unit Area ◽  
Zone Model ◽  
Smoke Control ◽  
Control Manner ◽  
High Rise ◽  
High Rise Building

The mechanical smoke exhaust is as acknowledged as an effective smoke control manner by making use of some necessary exhaust facilities. In this paper, a field model with a combination of a zone model were used to simulate the mechanical smoke exhaust in a loop corridor of the fire floor in a high-rise hotel, for the propose of evaluate fire safety of mechanical smoke exhaust. There were several factors are under discussion, as the arrangement of smoke vents, quantity of smoke vents, the volume of smoke exhaust, the position of the smoke vents and height of ceiling indoor, et al. The conclusions were obtained as followed. When two exhaust vents were set symmetrically in the loop corridor, one of which was located nearby the fire room, the smoke exhausted better. The volume of smoke exhaust per unit area with 60m3/h according to regulations, always could ensure safety of smoke exhaust.

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