A design basis tornado

1991 ◽  
Vol 18 (3) ◽  
pp. 521-524 ◽  
Author(s):  
Michael J. Newark
Keyword(s):  
Pressure Drop ◽  
Key Words ◽  
Rotational Speed ◽  
Static Pressure ◽  
Wind Pressure ◽  
Damage Area ◽  
Design Basis ◽  
Pressure Maximum ◽  
Translational Speed

Based on a combination of data from Canadian and U.S. sources, a design basis tornado is proposed for each of the five Fujita-scale categories (F0 to F4) of damage experienced in Canada. The parameters given are median damage length; median damage width; median damage area; maximum rotational speed; average translational speed; dynamic wind pressure; maximum static pressure drop; and the change of static pressure. Key words: design, tornado, structures, wind.

Experimental and Numerical Investigations on the Leakage Flow Characteristics of Helical-Labyrinth-Brush Seals

2020 ◽  
Author(s):  
Yuanqiao Zhang ◽  
Jun Li ◽  
Dengqian Ma ◽  
Yuan He ◽  
Jingjin Ji ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Rotational Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Leakage Flow ◽  
Absolute Value ◽  
Numerical Investigations ◽  
Brush Seal ◽  
Speed Up

Abstract This paper numerically investigates the leakage flow characteristics of two types of HLBSs (bristle pack installed upstream or downstream of helical-labyrinth tooth named as HLBS-U and HLBS-D, respectively) at various pressure ratios (1-1.3) and rotational speeds (0-10000r/min). In parallel, the leakage flow characteristics of the HLBS-D with the constant cb of 1.0 mm are experimentally measured at the pressure ratio up to 1.3 and rotational speed up to 2000 r/min. The effective clearance of the HLBS-U is smaller than that of the HLBS-D in the case of cb=0.5mm and rotational speed n<10000r/min, and the case of cb=1.0mm. However, for the case of cb=0.5mm and n=10000r/min, and the case of cb=0.1mm, the situation is opposite. The brush seal sections of the HLBS-U and the HLBS-D offer over 55% and 65% total static pressure drop in the case of cb=1.0 mm, respectively; The brush seal sections of two HLBSs bear almost the same static pressure drop of the over 97% total static pressure drop as cb equals to 0.1 mm. The HLBS-U has lower turbulent kinetic energy upstream of the bristle pack than the HLBS-D does, which means that intensity of bristles flutter of the HLBS-U is lower. The HLBS-U possesses significantly lower absolute value of aerodynamic forces than the HLBS-D does as cb=1.0 mm.

Experimental and Computational Analyses of Pressure Differentials in Flexible Ducts With Different Bent Angles

2007 ◽  
Author(s):  
Ray R. Taghavi ◽  
Wonjin Jin ◽  
Mario A. Medina
Keyword(s):  
Pressure Drop ◽  
Static Pressure ◽  
Complex Geometry ◽  
Analysis Data ◽  
Secondary Flows ◽  
Low Flow ◽  
Pressure Drops ◽  
Pressure Distributions ◽  
Geometrical Effects ◽  
Cfd Analyses

A set of experimental analyses was conducted to determine static pressure drops inside non-metallic flexible, spiral wire helix core ducts, with different bent angles. In addition, Computational Fluid Dynamics (CFD) solutions were performed and verified by comparing them to the experimental data. The CFD computations were carried out to produce more systematic pressure drop information through these complex-geometry ducts. The experimental setup was constructed according to ASHRAE Standard 120-1999. Five different bent angles (0, 30, 45, 60, and 90 degrees) were tested at relatively low flow rates (11 to 89 CFM). Also, two different bent radii and duct lengths were tested to study flexible duct geometrical effects on static pressure drops. FLUENT 6.2, using RANS based two equations - RNG k-ε model, was used for the CFD analyses. The experimental and CFD results showed that larger bent angles produced larger static pressure drops in the flexible ducts. CFD analysis data were found to be in relatively good agreement with the experimental results for all bent angle cases. However, the deviations became slightly larger at higher velocity regimes and at the longer test sections. Overall, static pressure drop for longer length cases were approximately 0.01in.H2O higher when compared to shorter cases because of the increase in resistance to the flow. Also, the CFD simulations captured more pronounced static pressure drops that were produced along the sharper turns. The stronger secondary flows, which resulted from higher and lower static pressure distributions in the outer and inner surfaces, respectively, contributed to these higher pressure drops.

Measurements of the nearly isotropic turbulence behind a uniform jet grid

1974 ◽  
Vol 62 (1) ◽  
pp. 115-143 ◽  
Author(s):  
Mohamed Gad-El-Hak ◽  
Stanley Corrsin
Keyword(s):  
Pressure Drop ◽  
Kinetic Energy ◽  
Static Pressure ◽  
Isotropic Turbulence ◽  
Decay Rates ◽  
Turbulence Energy ◽  
Turbulence Level ◽  
Average Force ◽  
General Behaviour ◽  
Decay Behaviour

Wind-tunnel turbulence behind a parallel-rod grid with jets evenly distributed along each rod is nearly isotropic. Homogeneity improvement over prior related experiments was attained by the use of controllable nozzles. Compared with the ‘passive’ case, the downwind-jet ‘active’ grid has a smaller static pressure drop across it and gives a smaller turbulence level at a prescribed distance from it, while the upwind-jet grid gives a larger static pressure drop and larger turbulence level. ‘Counterflow injection’ generates larger turbulence energy and larger scales, both events being evidently associated with instability of the jet system. This behaviour is much like that commonly observed behind passive grids of higher solidities.If the turbulent kinetic energy is approximated as an inverse power law in distance, the (positive) exponent decreases with increasing (downwind or upwind) jet strength, corresponding to slower absolute decay rates. No peculiar decay behaviour occurs when the jet grid is ‘self-propelled’ (zero net average force), or when the static pressure drop across it is zero.The injection does not change the general behaviour of the energy spectra, although the absolute spectra change inasmuch as the turbulence kinetic energy changes.

High Speed Flow Through Wire Gauzes

1959 ◽  
Vol 63 (584) ◽  
pp. 474-475 ◽  
Author(s):  
P. G. Morgan
Keyword(s):  
Pressure Drop ◽  
Pressure Loss ◽  
High Speed ◽  
Static Pressure ◽  
Flow Conditions ◽  
High Speed Flow ◽  
Speed Flow ◽  
Wire Gauze ◽  
Flow Through

The Flow of Fluids through screens has been widely studied with particular importance being attached to the measurement of the pressure drop caused by a screen and its relation to the screen geometry and the flow conditions. The majority of the investigations have been carried out on wire gauze screens mounted in ducts with air passing through them, the static pressure being measured on either side of the gauze. Attempts have been made by Weighardt Annand and Grootenhuisto correlate the gauze geometry with the pressure drop and to enable the pressure loss over a given screen and with given flow conditions to be predicted.

Internal flow analysis of a porous burner via CFD

2019 ◽  
Vol 29 (8) ◽  
pp. 2666-2683 ◽  
Author(s):  
Ali H. Abdulkarim ◽  
Ali Ates ◽  
Kemal Altinisik ◽  
Eyüb Canli
Keyword(s):  
Pressure Drop ◽  
Static Pressure ◽  
Porous Metal ◽  
Cfd Analysis ◽  
Flow Conditions ◽  
Content Type ◽  
Flow Mixing ◽  
Porous Burner ◽  
Flow Domain ◽  
Burner Design

Purpose This study aims to introduce a metal porous burner design. Literature is surveyed in a comprehensive manner to relate the current design with ongoing research. A demonstrative computational fluid dynamics (CFD) analysis is presented with projected flow conditions by means of a common commercial CFD code and turbulence model to show the flow-related features of the proposed burner. The porous metal burner has a novel design, and it is not commercially available. Design/methodology/approach Based on the field experience about porous burners, a metal, cylindrical, two-staged, homogenous porous burner was designed. Literature was surveyed to lay out research aspects for the porous burners and porous media. Three dimensional solid computer model of the burner was created. The flow domain was extracted from the solid model to use in CFD analysis. A commercial computational fluid dynamics code was utilized to analyze the flow domain. Projected flow conditions for the burner were applied to the CFD code. Results were evaluated in terms of homogenous flow distribution at the outer surface and flow mixing. Quantitative results are gathered and are presented in the present report by means of contour maps. Findings There aren’t any flow sourced anomalies in the flow domain which would cause an inefficient combustion for the application. An accumulation of gas is evident around the top flange of the burner leading to higher static pressure. Generally, very low pressure drop throughout the proposed burner geometry is found which is regarded as an advantage for burners. About 0.63 Pa static pressure increase is realized on the flange surface due to the accumulation of the gas. The passage between inner and outer volumes has a high impact on the total pressure and leads to about 0.5 Pa pressure drop. About 0.03 J/kg turbulent kinetic energy can be viewed as the highest amount. Together with the increase in total enthalpy, total amount of energy drawn from the flow is 0.05 J/kg. More than half of it spent through turbulence and remaining is dissipated as heat. Outflow from burner surface can be regarded homogenous though the top part has slightly higher outflow. This can be changed by gradually increasing pore sizes toward inlet direction. Research limitations/implications Combustion via a porous medium is a complex phenomenon since it involves multiple phases, combustion chemistry, complex pore geometries and fast transient responses. Therefore, experimentation is used mostly. To do a precise computational analysis, strong computational power, parallelizing, elaborate solid modeling, very fine meshes and small time steps and multiple models are required. Practical implications Findings in the present work imply that a homogenous gas outflow can be attained through the burner surfaces while very small pressure drop occurs leading to less pumping power requirement which is regarded as an advantage. Flow mixing is realizable since turbulent kinetic energy is distinguished at the interface surface between inner and outer volumes. The porous metal matrix burner offers fluid mixing and therefore better combustion efficiency. The proposed dimensions are found appropriate for real-world application. Originality/value Conducted analysis is for a novel burner design. There are opportunities both for scientific and commercial fields.

Static Pressure Drop Across a Bed of Corn Mixed with Fines

1978 ◽  
Vol 21 (5) ◽  
pp. 0997-1000 ◽  
Author(s):  
E. Haque ◽  
G. H. Foster ◽  
D. S. Chung ◽  
p s. Lai
Keyword(s):  
Pressure Drop ◽  
Static Pressure

Aerodynamic Torque Acting on a Butterfly Valve. Comparison and Choice of a Torque Coefficient

1999 ◽  
Vol 121 (4) ◽  
pp. 914-917 ◽  
Author(s):  
C. Solliec ◽  
F. Danbon
Keyword(s):  
Pressure Drop ◽  
Static Pressure ◽  
Fluid Dynamic ◽  
Dynamic Pressure ◽  
Low Cost ◽  
Normalization Method ◽  
Pressure Drops ◽  
Torque Coefficient ◽  
Aerodynamic Torque ◽  
Valve Pressure

Most technological devices use butterfly valves to check the flow rate and speed, through piping. Their main advantages are their low cost, their mechanical suitability for fast operation, and their small pressure drops when they are fully open. The fluid dynamic torque about the axis of large valves has to be considered as the actuator could be overstrained. This torque is generally defined using a nondimensional coefficient KT, in which the static pressure drop created by the valve is used for normalization. When the valve is closed downstream of an elbow, the valve pressure drop is not well defined. Thus, the classic normalization method gives many ambiguities. To avoid the use of the pressure drop, we define another torque coefficient CT in which the dynamic pressure of the flow is the normalization factor instead of the pressure drop. Advantages and drawbacks of each normalization method are described in the following.

Experimental Observations on the Thermal Performance of a Rotating Coolant Circuit with Reference to the Design of Electrical Machine Rotors

1976 ◽  
Vol 190 (1) ◽  
pp. 561-570 ◽  
Author(s):  
W. D. Morris ◽  
F. M. Dias
Keyword(s):  
Energy Dissipation ◽  
Pressure Drop ◽  
Thermal Performance ◽  
Rotational Speed ◽  
Electrical Machines ◽  
Hydrodynamic Characteristics ◽  
Electrical Machine ◽  
Coolant Circuit

SYNOPSIS This paper presents the results of an investigation into the influence of rotation on the thermal and hydrodynamic characteristics of a rotating coolant circuit which has relevance to the design of cooled rotors for electrical machines. Tests conducted with a fixed pressure drop across the entire rotor circuit demonstrate that increases in rotational speed can produce consequential increases in the temperature of the simulated winding. This is true for the case where the energy dissipation is constant.

Pressure Analysis of Airflow With Different Inlet Angle in the Oblique Rectangular Fin Channels

2016 ◽  
Author(s):  
Zhiying Liu ◽  
Hui Li ◽  
Lin Shi ◽  
Yangjun Zhang ◽  
Ruixia Li ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Static Pressure ◽  
Slope Angle ◽  
Rapid Change ◽  
Three Dimensional ◽  
Leeward Side ◽  
Numerical Work ◽  
Section Shape ◽  
Flow Length ◽  
Inlet Angle

Previous work about the oblique fin channels shows an abnormal variation on the static pressure drop. Thus numerical work was performed to investigate the influence of the lengthwise distance and the parallelogrammic fin section shape separately using two groups of fin mesh. The results showed that the influence of the parallelogrammic fin section shape was similar to the three-dimensional oblique fin channels. Besides, when air flow is askew to the fin, there is a vortex near the leeward side. The pressure had a rapid change in the entrance and vortex region and then decreased linearly along the flow length. The static pressure drop in the vortex region is determined by both the fin slope angle and the inlet angle. Thus the variation law of oblique fin channels is different from the straight fin channels.

Biofiltration de l'air pollué par le xylène : observations expérimentales

2002 ◽  
Vol 29 (4) ◽  
pp. 543-553 ◽  
Author(s):  
Hasnaa Jorio ◽  
Guy Viel ◽  
Michèle Heitz
Keyword(s):  
Carbon Dioxide ◽  
Pressure Drop ◽  
Key Words ◽  
Removal Efficiency ◽  
Residence Time ◽  
Elimination Capacity ◽  
Nutritive Solution ◽  
Filter Bed ◽  
Empty Bed Residence Time

A new filtering material has been tested for its biofiltration performance for the treatment of air contaminated with the three isomers of xylene. The biofilter, operated at an empty bed residence time of 68 s and for xylene concentrations up to 6.7 g·m–3, allowed a xylene load and reduction of more than 92% for concentrations up to 2 g·m–3, and more than 65% for concentrations less than 6.7 g·m–3. The maximum xylene elimination capacity is of 236 g·m–3·h–1. In general, the removal efficiency of meta-xylene is the highest whereas the removal efficiency of ortho-xylene is the lowest. At high xylene concentration, the increase of biodegradation intensity leads to the accumulation of a voluminous biofilm around the filtering particles, causing the clogging of the filter bed, the progressive retention of the nutritive solution in the superior parts of the bed, and the drying of the inferior parts of the bed. These observations have showed that a biofilter operating at high elimination capacities requires a meticulous control of the humidity of the filtering bed and a regular draining of the biomass excess. Key words: biofiltration, xylene, ortho, meta, and para isomers, carbon dioxide, biofilm, pressure drop, biomass excess.[Journal translation]

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