THE WIND TUNNEL DEVELOPMENT OF A PROPOSED EXTERNAL FORM FOR STEAM LOCOMOTIVES

1933 ◽  
Vol 8 (1) ◽  
pp. 37-61
Author(s):  
J. J. Green
Keyword(s):  
Wind Tunnel ◽  
Maximum Degree ◽  
Air Flow ◽  
Forward Direction ◽  
The Body ◽  
Air Resistance ◽  
Clean Air ◽  
Work Done ◽  
External Form ◽  
External Shape

The existing shape and arrangement of steam locomotives are such that smoke from the stack tends to sweep back along the boiler top and descend in front of the cab windows, seriously impairing forward vision. For the maximum degree of safety it is essential that the view from the cab, especially in a forward direction, should be unobstructed at all times. It is therefore desirable that some means be found for improving the manner in which the smoke is carried away from the stack. In addition to preventing the descent of smoke at the cab it is desirable that the external shape of the locomotive should be so modified as to result in a decreased air resistance, in view of the growing demand for economical running at increasingly higher speeds.The paper describes work done in the wind tunnel of the National Research Laboratories and discusses the steps whereby an improved external shape has been evolved for locomotives such that the smoke is lifted over the cab thus making possible an unimpaired vision ahead.The new design is the result of the application of elementary aerodynamics to the problem and aims at providing smoother air flow about the locomotive. Further, a layer of clean air is introduced between the smoke and the body of the locomotive and is responsible for maintaining the smoke above the cab. By removing the violent eddying flow about the locomotive the air resistance of the engine and tender has been reduced to the extent of some 35%.

scholarly journals Wind tunnel for studies of latent heat storage

2018 ◽  
Vol 180 ◽  
pp. 02108 ◽  
Author(s):  
Václav Tesař
Keyword(s):  
Wind Tunnel ◽  
Test Section ◽  
Air Flow ◽  
The Body ◽  
Whole Body ◽  
Latent Heat Storage ◽  
Hot Air ◽  
Cold Room ◽  
Solidification Processes ◽  
Sudden Decrease

When a heated solid body temperature reaches the melting point, temperature stops increasing and remains constant until the whole body is completely molten. The heat input during this melting is spent on freeing the body molecules. This latent heat of melting remains inside the body and may be released when the body is cooled and solidifies. This heat was suggested, already several decades ago, for storing thermal energy. The advantage it offers is avoiding high temperature differences - which otherwise decrease effectiveness of storage (by inevitable heat escape by conduction). Also the mass of the body needed to store a given amount of heat is much smaller. For investigations of the melting and solidification processes a special wind tunnel has been designed and is being built in this study. The tested sample of phase change material, encapsulated in a spherical shell, will be exposed in the tunnel to recirculating hot air flow in a 140 mm x 140 mm test section. Sudden decrease in air flow temperature is made by shifting away the whole closed-circuit part of the tunnel and exposing the test section to flow of cold (room temperature) air.

scholarly journals Aerodynamics of Cycling Skinsuits Focused on the Surface Shape of the Arms

2021 ◽  
Vol 11 (5) ◽  
pp. 2200
Author(s):  
Sungchan Hong ◽  
Takeshi Asai
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Experiment ◽  
The Body ◽  
Surface Shape ◽  
Air Resistance ◽  
Computational Fluid Dynamics Cfd ◽  
Race Conditions ◽  
Cfd Method ◽  
Fabric Surface ◽  
Full Body

In cycling, air resistance corresponds to 90% of the resistance on the bicycle and cyclist and 70% of this is applied to the body of the cyclist. Despite research on postures that could reduce air resistance, few studies have been conducted on full-body cycling suits. As the aerodynamics of the surface shape of clothing fabric are still unclear, the airflow around cyclists and air resistance were examined using a computational fluid dynamics (CFD) method and wind tunnel experiment. Specifically, in this study, we focused on how different surface shapes of cycling suit fabrics affect air resistance. CFD results indicate that air resistance during a race was high at the head, arms and legs of the cyclist. In the wind tunnel experiment, a cylinder model resembling the arms was used to compare the aerodynamic forces of various fabrics and the results showed that air resistance changed according to the fabric surface shape. Moreover, by changing the fabric shape of the arms of the cycling suits, reduction of air resistance by up to 8% is achievable. These results suggest that offering the most appropriate suit type to each cyclist, considering race conditions, can contribute to further improvement in their performance.

Mechanical work in terrestrial locomotion: two basic mechanisms for minimizing energy expenditure

1977 ◽  
Vol 233 (5) ◽  
pp. R243-R261 ◽  
Author(s):  
G. A. Cavagna ◽  
N. C. Heglund ◽  
C. R. Taylor
Keyword(s):  
Center Of Mass ◽  
Forward Direction ◽  
Gravitational Energy ◽  
The Body ◽  
Unit Weight ◽  
Gravitational Potential Energy ◽  
Terrestrial Locomotion ◽  
Energy Conserving ◽  
Walking Speeds ◽  
Work Done

The work done during each step to lift and to reaccelerate (in the forward direction) and center of mass has been measured during locomotion in bipeds (rhea and turkey), quadrupeds (dogs, stump-tailed macaques, and ram), and hoppers (kangaroo and springhare). Walking, in all animals (as in man), involves an alternate transfer between gravitational-potential energy and kinetic energy within each stride (as takes place in a pendulum). This transfer is greatest at intermediate walking speeds and can account for up to 70% of the total energy changes taking place within a stride, leaving only 30% to be supplied by muscles. No kinetic-gravitational energy transfer takes place during running, hopping, and trotting, but energy is conserved by another mechanism: an elastic “bounce” of the body. Galloping animals utilize a combination of these two energy-conserving mechanisms. During running, trotting, hopping, and galloping, 1) the power per unit weight required to maintain the forward speed of the center of mass is almost the same in all the species studied; 2) the power per unit weight required to lift the center of mass is almost independent of speed; and 3) the sum of these two powers is almost a linear function of speed.

Air flow quality analysis of an open-circuit boundary layer wind tunnel and comparison with a closed-circuit wind tunnel

2020 ◽  
Vol 32 (12) ◽  
pp. 125120
Author(s):  
María Jiménez-Portaz ◽  
Luca Chiapponi ◽  
María Clavero ◽  
Miguel A. Losada
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Air Flow ◽  
Open Circuit ◽  
Closed Circuit ◽  
Quality Analysis ◽  
Flow Quality

Rack Level Modeling of Air Flow Through Perforated Tile in a Data Center

2012 ◽  
Author(s):  
Vaibhav K. Arghode ◽  
Pramod Kumar ◽  
Yogendra Joshi ◽  
Thomas S. Weiss ◽  
Gary Meyer
Keyword(s):  
Data Center ◽  
Body Force ◽  
Air Flow ◽  
The Body ◽  
Physical Models ◽  
Cfd Modeling ◽  
Computational Time ◽  
Force Model ◽  
Flow Through ◽  
Tile Surface

Effective air flow distribution through perforated tiles is required to efficiently cool servers in a raised floor data center. We present detailed computational fluid dynamics (CFD) modeling of air flow through a perforated tile and its entrance to the adjacent server rack. The realistic geometrical details of the perforated tile, as well as of the rack are included in the model. Generally models for air flow through perforated tiles specify a step pressure loss across the tile surface, or porous jump model based on the tile porosity. An improvement to this includes a momentum source specification above the tile to simulate the acceleration of the air flow through the pores, or body force model. In both of these models geometrical details of tile such as pore locations and shapes are not included. More details increase the grid size as well as the computational time. However, the grid refinement can be controlled to achieve balance between the accuracy and computational time. We compared the results from CFD using geometrical resolution with the porous jump and body force model solution as well as with the measured flow field using Particle Image Velocimetry (PIV) experiments. We observe that including tile geometrical details gives better results as compared to elimination of tile geometrical details and specifying physical models across and above the tile surface. A modification to the body force model is also suggested and improved results were achieved.

A Roundabout for Studying Sustained Flight of Locusts

1952 ◽  
Vol 29 (2) ◽  
pp. 211-219 ◽  
Author(s):  
AUGUST KROGH ◽  
TORKEL WEIS-FOGH
Keyword(s):  
Wind Tunnel ◽  
External Factors ◽  
Flight Performance ◽  
Average Speed ◽  
Preliminary Results ◽  
Air Resistance

A roundabout technique is described which makes it possible to study the flight performance of a small ‘swarm’ of locusts (up to thirty-two individuals) for hours at a time. The resistance of the roundabout was compensated by means of a mill so that the locusts only had to overcome their own air resistance. The speed of the revolving periphery therefore equalled the preferred average flying speed of the suspended locusts. The average speed during a period, as well as the variation in speed in the course of an experiment, were found to be the same in the roundabout and in experiments where single locusts flew in front of a wind tunnel. In the latter case the insects flew in completely normal flight posture. It was concluded that the results obtained with the roundabout were as valid as the results obtained with a wind tunnel. Some preliminary results are given on the influence of different external factors on the flying speed and the ability to endure sustained flight.

THE EFFECTS OF ALTERED AQUATIC AND AERIAL RESPIRATORY GAS CONCENTRATIONS ON AIR-BREATHING PATTERNS IN A PRIMITIVE FISH (AMIA CALVA)

1993 ◽  
Vol 181 (1) ◽  
pp. 81-94 ◽  
Author(s):  
M. S. Hedrick ◽  
D. R. Jones
Keyword(s):  
Air Flow ◽  
The Body ◽  
Type I ◽  
Type Ii ◽  
Breathing Frequency ◽  
Breathing Patterns ◽  
Flow Measurements ◽  
Air Breathing ◽  
Gas Bladder ◽  
Amia Calva

The mechanisms and physiological control of air-breathing were investigated in an extant halecomorph fish, the bowfin (Amia calva). Air flow during aerial ventilation was recorded by pneumotachography in undisturbed Amia calva at 20–24°C while aquatic and aerial gas concentrations were independently varied. Separation of aquatic and aerial gases was used in an attempt to determine whether Amia calva monitor and respond to changes in the external medium per se or to changes in dissolved gases within the body. Air flow measurements revealed two different types of ventilatory patterns: type I air-breaths were characterized by exhalation followed by inhalation; type II air-breaths, which have not been described previously in Amia calva, consisted of single inhalations with no expiratory phase. Expired volume (Vexp) for type I breaths ranged from 11.6+/−1.1 to 26.7+/− 2.9 ml kg-1 (95 % confidence interval; N=6) under normoxic conditions and was unaffected by changes in aquatic or aerial gases. Gas bladder volume (VB), determined in vitro, was 80 ml kg-1; the percentage of gas exchanged for type I breaths ranged from 14 to 33 % of VB in normoxia. Fish exposed to aquatic and aerial normoxia (PO2=19-21 kPa), or aerial hypercapnia (PCO2=4.9 kPa) in normoxic water, used both breath types with equal frequency. Aquatic or aerial hypoxia (PO2=6-7 kPa) significantly increased air-breathing frequency in four of eight fish and the ventilatory pattern changed to predominantly type I air-breaths (75–92 % of total breaths). When fish were exposed to 100 % O2 in the aerial phase while aquatic normoxia or hypoxia was maintained, air-breathing frequency either increased or did not change. Compared with normoxic controls, however, type II breaths were used almost exclusively (more than 98 % of total breaths). Type I breaths appear to be under feedback control from O2-sensitive chemoreceptors since they were stimulated by aquatic or aerial hypoxia and were nearly abolished by aerial hyperoxia. These results also indicate that Amia calva respond to changes in intravascular PO2; however, externally facing chemoreceptors that stimulate air-breathing in aquatic hypoxia cannot be discounted. Type II air- breaths, which occurred in aerial hyperoxia, despite aquatic hypoxia, appear to be stimulated by reductions of VB, suggesting that type II breaths are controlled by volume-sensitive gas bladder stretch receptors. Type II breaths are likely to have a buoyancy-regulating function.

scholarly journals Full-Span Flying Wing Wind Tunnel Test: A Body Freedom Flutter Study

Fluids ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 34
Author(s):  
Pengtao Shi ◽  
Jihai Liu ◽  
Yingsong Gu ◽  
Zhichun Yang ◽  
Pier Marzocca
Keyword(s):  
Wind Tunnel ◽  
Theoretical Analysis ◽  
Mass Balance ◽  
Degrees Of Freedom ◽  
Wind Tunnel Test ◽  
Suspension System ◽  
The Body ◽  
Structural Dynamic ◽  
Flutter Speed ◽  
Theoretical Results

Aiming at the experimental test of the body freedom flutter for modern high aspect ratio flexible flying wing, this paper conducts a body freedom flutter wind tunnel test on a full-span flying wing flutter model. The research content is summarized as follows: (1) The full-span finite element model and aeroelastic model of an unmanned aerial vehicle for body freedom flutter wind tunnel test are established, and the structural dynamics and flutter characteristics of this vehicle are obtained through theoretical analysis. (2) Based on the preliminary theoretical analysis results, the design and manufacturing of this vehicle are completed, and the structural dynamic characteristics of the vehicle are identified through ground vibration test. Finally, the theoretical analysis model is updated and the corresponding flutter characteristics are obtained. (3) A novel quasi-free flying suspension system capable of releasing pitch, plunge and yaw degrees of freedom is designed and implemented in the wind tunnel flutter test. The influence of the nose mass balance on the flutter results is explored. The study shows that: (1) The test vehicle can exhibit body freedom flutter at low airspeeds, and the obtained flutter speed and damping characteristics are favorable for conducting the body freedom flutter wind tunnel test. (2) The designed suspension system can effectively release the degrees of freedom of pitch, plunge, and yaw. The flutter speed measured in the wind tunnel test is 9.72 m/s, and the flutter frequency is 2.18 Hz, which agree well with the theoretical results (with flutter speed of 9.49 m/s and flutter frequency of 2.03 Hz). (3) With the increasing of the mass balance at the nose, critical speed of body freedom flutter rises up and the flutter frequency gradually decreases, which also agree well with corresponding theoretical results.

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