Aerodynamic and thermal characteristics of a body of complex shape around which a hypersonic air stream flows

1987 ◽  
Vol 52 (4) ◽  
pp. 391-395
Author(s):  
S. V. Peigin ◽  
V. G. Postnikov
Keyword(s):  
Complex Shape ◽  
Thermal Characteristics ◽  
Stream Flows ◽  
Air Stream

scholarly journals Application of numerical modelling in stream metrology on the example of primary air installation

2019 ◽  
Vol 82 ◽  
pp. 01006
Author(s):  
Mirosław Kabaciński ◽  
Janusz Pospolita ◽  
Janusz Polak ◽  
Piotr Adamus ◽  
Antoni Salij ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Measurement Problem ◽  
Dynamic Pressure ◽  
Flow Simulation ◽  
Measuring System ◽  
Problem Solution ◽  
System Operation ◽  
Stream Flows ◽  
Flow Disturbances ◽  
Air Stream

Measurements of stream flows are very common in the power industry. High parameters of the fluid, its impurities or the complexity of the flow installation make often such measurement problematic. Flow disturbances are a factor that significantly increases measurement uncertainty. The paper presents an example the measurement problem solution based on mathematical modelling and digital flow simulation. The problem was the measurement of the air stream in a complex mill air flow installation. A measuring system based on a probe averaging dynamic pressure has been developed. The location of the probe was determined by numerically modelling the flow in the considered section of the mill air installation. Monthly observations of the measuring system operation confirmed its high usefulness in the operation of the mill installation.

scholarly journals Thermo-Hydraulic Performance of Solar Air Collectors with Artificially Roughened Absorbers: A Comparative Review of Semi-Empirical Models

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3536 ◽  
Author(s):  
António Araújo
Keyword(s):  
Heat Transfer ◽  
Thermal Characteristics ◽  
Operating Conditions ◽  
Roughness Parameters ◽  
Energy Characteristics ◽  
Effective Roughness ◽  
Air Stream ◽  
Comparative Review ◽  
Efficiency And Effectiveness ◽  
Semi Empirical

Due to the poor thermal characteristics of the air, the absorber roughness of solar air collectors is commonly artificially increased in order to enhance the heat transfer to the air stream. However, this is also accompanied by an undesirable increase in the pumping power due to increased friction losses. As a result, several authors have experimentally investigated several ways of maximizing the heat transfer while minimizing the friction losses of different absorbers, resulting in the development of semi-empirical functions relating the Nusselt number (a measure of heat transfer) and the friction factor (a measure of friction losses) to the Reynolds number and the roughness parameters considered for each absorber. The present paper reviews, considering the publications from the last ten years, these semi-empirical functions. Moreover, the optimum roughness parameters and operating conditions of the absorbers were estimated by finding the maximum values of two performance parameters (the thermo-hydraulic efficiency and effectiveness), calculated using the semi-empirical functions, in order to classify the absorbers in terms of their energy characteristics. This approach proves to be a rather effective way of optimizing the roughness characteristics of solar air collector absorbers. It is also concluded that, considering the range of absorbers analyzed here, generally, multiple V-shaped ribs with gaps provide the most effective roughness geometry.

scholarly journals STUDY OF THE EFFECT OF COMPLEX-COMPOSITE STRUCTURES ON THE THERMAL CHARACTERISTICS OF THE POLYMER ADDITIVE MATERIALS

2019 ◽  
Vol 45 (4) ◽  
pp. 8-17
Author(s):  
N. V. Bekrenev ◽  
V. M. Makarova ◽  
S. P. Pavlov
Keyword(s):  
Thermal Conductivity ◽  
Composite Material ◽  
Carbon Fibers ◽  
Composite Structures ◽  
Complex Shape ◽  
Experimental Studies ◽  
Thermal Characteristics ◽  
Additive Technologies ◽  
Mechanical And Thermal Properties ◽  
Additive Materials

Objectives The use of additive technologies is one of the promising areas for improving the production of products for various purposes in the transition to a digital economy. Method. Layered construction of objects of complex shape in accordance with the developed solid-state model from materials with different mechanical and thermal properties allows directionally controlling the distribution of various components in the volume of the composite material and forming topological structures that provide a rational balance between various performance characteristics and reliability of the product. Result. Based on experimental studies, it has been established that reinforcing topological reinforcement of 3D printing objects made from ABS plastic with a composite consisting of carbon fibers and ED-20 epoxy resin, along with an increase in flexural strength and tensile strength, contributes to an increase in thermal conductivity of the material by more than 18% and thermal diffusivity - by 20%. A computer simulation of elementary cells of a composite material consisting of a polymer matrix, carbon fiber and special core inclusions with high thermal conductivity was performed, which made it possible to further increase thermal conductivity depending on the relative fiber diameter and the percentage of the additional component in an amount from 46 to 75%. Conclusion It is shown that additive technologies are an effective tool for creating universal topologies that allow technologically managing a combination of both mechanical and thermophysical properties of structural materials by determining the rational relative position of their components depending on the purpose and level of achievement of the required characteristics. 

Wind-generated waves in thin liquid films with soluble contaminant

1971 ◽  
Vol 45 (3) ◽  
pp. 527-544 ◽  
Author(s):  
F. I. P. Smith ◽  
Alex D. D. Craik
Keyword(s):  
Surface Active Agent ◽  
Active Agent ◽  
Theoretical Work ◽  
Liquid Films ◽  
Stream Flows ◽  
Surface Active Agents ◽  
Air Stream ◽  
Surface Active ◽  
The Stability

Craik (1968) has previously examined the stability of horizontal liquid films when an air stream flows over the liquid surface and when the surface is contaminated by an insoluble surface-active agent. The present theoretical work extends this investigation to examine the role of soluble surface-active agents for cases where the liquid Reynolds number is small. This role is found to be a rather complex one which, under suitable conditions, may be either stabilizing or destabilizing.Related experimental work is described which yields results in qualitative agreement with the theoretical analysis.

On the Configuration of the Magnetic Field of β CrB

1976 ◽  
Vol 32 ◽  
pp. 613-622
Author(s):  
I.A. Aslanov ◽  
Yu.S. Rustamov
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Radial Velocity ◽  
Magnetic Field Strength ◽  
Complex Shape ◽  
Rotation Period ◽  
Field Variation ◽  
Magnetic Field Variation ◽  
Secular Variations ◽  
The Magnetic Field

SummaryMeasurements of the radial velocities and magnetic field strength of β CrB were carried out. It is shown that there is a variability with the rotation period different for various elements. The curve of the magnetic field variation measured from lines of 5 different elements: FeI, CrI, CrII, TiII, ScII and CaI has a complex shape specific for each element. This may be due to the presence of magnetic spots on the stellar surface. A comparison with the radial velocity curves suggests the presence of a least 4 spots of Ti and Cr coinciding with magnetic spots. A change of the magnetic field with optical depth is shown. The curve of the Heffvariation with the rotation period is given. A possibility of secular variations of the magnetic field is shown.

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