scholarly journals Thermal-Hydrodynamic Characteristics of Turbulent Flow in Corrugated Channels

2020 ◽  
Author(s):  
Nabeel S. Dhaidana ◽  
Abdalrazzaq K. Abbas
Keyword(s):  
Turbulent Flow ◽  
Hydrodynamic Characteristics

scholarly journals HYDRODYNAMICS, DISTRIBUTION OF FLOWS AND THERMAL EFFICIENCY OF COIL HEAT EXCHANGERS IN UNITS OF HEAT-USING APPARATUS OF TUBE FURNACES

2019 ◽  
Vol 62 (4) ◽  
pp. 143-151
Author(s):  
Stanislav P. Sergeev ◽  
Faddey F. Nikiforov ◽  
Sergey V. Afanasiev ◽  
Juliya N. Shevchenko
Keyword(s):  
Heat Exchange ◽  
Turbulent Flow ◽  
Thermal Efficiency ◽  
Heat Exchangers ◽  
Heat Fluxes ◽  
Hydrodynamic Characteristics ◽  
Technological Problem ◽  
Tube Furnaces ◽  
Suction Or Injection ◽  
Coil Heat

The theoretical foundations of construction, mathematical description and engineering calculation of heat exchangers of the serpentine type in blocks of heat-using equipment of tube furnaces and other types of reactors designed for carrying out endothermic reactions (in particular, reforming of natural gas with water vapor) are considered. It is shown that the thermal efficiency of heat exchangers of the coil type is significantly affected by the correct choice of parameters ensuring a uniform distribution of energy flows over the surface of heat-resistant heat exchange tubes. This technological problem is solved by compiling the heat balance and selecting the system of the corresponding equations, which allows to calculate the temperature contour of the coil heat exchanger, its hydrodynamic characteristics and the distribution of mass and heat flows through the heat exchange tubes. The use of the tensor form of the Boussinesq hypothesis is considered, with which the Reynolds equation describing a turbulent flow is transformed to a partial differential equation for a single unknown function and its averaged form is obtained. In relation to the problem under consideration, the correctness of the chosen approach was confirmed both theoretically and experimentally. It is shown that in the core of a turbulent flow with an intense suction or injection, the liquid behaves almost as ideal and the well-known Helmholtz – Friedmann theorem holds with the necessary accuracy. From the aforementioned averaged equation, expressions are obtained that are suitable for describing heat fluxes in channels with suction or injection. According to this theoretical model, thermal calculations of coil-type heat exchangers were carried out, a more accurate assessment of the temperature of the heated medium in each coil tube was made, and the temperature gradient of the external heat carrier over the cross section of the gas duct was found. For the first time in the practice of calculations when choosing the parameters of coils, a number of boundary conditions were taken into account, such as the condition of the coil layout, the necessary heat exchange surface, permissible restrictions on hydraulic resistance, etc.

Connection of the hydrodynamic characteristics of turbulent flow of a liquid with its maximum flow rate

1973 ◽  
Vol 16 (3) ◽  
pp. 466-467
Author(s):  
N. T. Fazullin ◽  
M. S. Fomichev ◽  
A. V. Popov ◽  
A. B. Isaev
Keyword(s):  
Turbulent Flow ◽  
Flow Rate ◽  
Maximum Flow ◽  
Maximum Flow Rate ◽  
Hydrodynamic Characteristics

Numerical Simulation of Turbulent Flow Around Podded Propeller in Azimuthing Conditions

2012 ◽  
Author(s):  
Reza Shamsi ◽  
Hassan Ghassemi
Keyword(s):  
Turbulent Flow ◽  
Open Water ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Characteristic Parameters ◽  
Hydrodynamic Analysis ◽  
Podded Propulsor ◽  
Performance Curves ◽  
Yaw Angle ◽  
Thrust And Torque

This paper investigates the numerical modeling of turbulent flow and hydrodynamic analysis of podded propeller in open water and azimuthing conditions. The RANS (Reynolds-Averaged Navier Stokes) based solver is used in order to study the variations of hydrodynamic characteristics of podded propeller at various angles. The variations of thrust and torque coefficients as functions of the advance coefficient are obtained at various yaw angles. Turbulent flow around the propeller and pod are presented. At first, the propeller is analyzed in open water condition in absence of pod and strut. Next flow around pod and strut are simulated without effect of propellers. Finally, the whole unit is studied in zero yaw angle and azimuthing condition. These investigations are performed for two podded propulsor configurations: puller and pusher. Total forces on the unit in each direction and propeller torque are computed for a range of advance coefficients from 0.2 to 1. Yaw angle of pod are modified from +15° to −15° by increments of 5°. Computational results are examined against with available experimental data. Characteristic parameters including torque and thrust of propeller, axial force, and side force of unit are presented as functions of advance coefficient and yaw angle. The performance curves of the propeller obtained by numerical method are compared and verified by the experimental results. The results show that the propeller thrust, torque, and podded unit forces and moments in azimuthing condition depend on propeller advance coefficient and yaw angle.

scholarly journals Study on the Nearshore Evolution of Regular Waves under Steady Wind

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 686 ◽  
Author(s):  
Changbo Jiang ◽  
Yang Yang ◽  
Bin Deng
Keyword(s):  
Wind Speed ◽  
Numerical Model ◽  
Turbulent Flow ◽  
Wave Breaking ◽  
Surface Wind ◽  
Average Level ◽  
Hydrodynamic Characteristics ◽  
Turbulent Dissipation ◽  
Cross Spectrum ◽  
The Cross

We present a study on regular wave propagation on a sloping bed under the action of steady wind, which is of a great significance to complement and replenish the interaction mechanisms of nearshore wave and wind. Physical experiments were conducted in a wind-wave flume, and the corresponding numerical model was constructed based on the solver Waves2FOAM in OpenFOAM, with large-eddy simulation (LES) used to investigate the turbulent flow. The comparisons between the measured and calculated results of the free surface elevation and flow velocity indicated that the numerical model could predict the associated hydrodynamic characteristics of a nearshore wave regardless of the presence or absence of wind. The results showed that wind had a significant impact on nearshore wave evolution. It was found that under the same wind speed coverage constraint, wave breaking occurred ahead of time. The smaller the surf similarity ξ 0 was, the higher the dispersion degree of wave breaking locations would be, and the breaker index of H b / h b increased with wind speed under the same incident wave height. The main components of analysis for turbulent flow were the results of the cross-spectrum, the TKE (turbulent kinetic energy), and TDR (turbulent dissipation rate). The cross-spectrum illustrated that wind enhanced the degree of coherence of the residual velocity components and aggravated turbulence. The TKE indicated that in regions near the water surface, wind speed made it considerably larger and the average level rapidly decreased with depth. The TDR exhibited that the significant effect of wind was merely imposed after breaking, wherein the turbulence penetrated the deeper flow and the average level generally rose. The velocity profile on the slope showed that the wind accelerated the undertow, and the moment statistics indicated that the velocity distribution deviated gradually from the Gaussian distribution to the right.

scholarly journals KARAKTERISTIK TERMAL HIDRODINAMIK UNTUK ALIRAN LAMINAR DAN TURBULEN DI DALAM PIPA DENGAN BERBAGAI BENTUK SISIPAN PLAT BERGALUR

ROTASI ◽  
2015 ◽  
Vol 17 (4) ◽  
pp. 182
Author(s):  
Syaiful Syaiful ◽  
Faza Dzulhimam
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Three Dimensional ◽  
Working Fluid ◽  
Hydrodynamic Characteristics ◽  
Transfer Enhancement ◽  
Three Dimensional Flow ◽  
Laminar And Turbulent Flow ◽  
Heat Transfer Improvement

The purpose of this study is to investigate the thermal and hydrodynamic characteristics of air flowing in tubes with various inserts of grooved plate. Inserts of grooved plate with a variety of attack angles (a = 0°, 45° and 90°) has been studied in laminar and turbulent flow. Plate inserts are installed inside the tube intended to improve the heat transfer due to the mixing of the fluid. Numerical simulation of three-dimensional flow set as a model in the direction of fluid flow. The working fluid in the tube is cold, whereas hot wall temperature is kept constant. The results showed that the grooved plate inserts increases the heat transfer in the tube. For laminar flow, the highest heat transfer enhancement is obtained at the grooved plate inserts α = 45° i.e. from 4.46 to 20.34% with an increase in friction factor of 172.19 to 204.36%. As for the turbulent flow, the highest heat transfer improvement is found in a grooved plate inserts with α = 45° i.e. from 38.67 to 56.1% with an increase in friction factor of 183.5 to 262.29%.

Measurement of the hydrodynamic characteristics of turbulent flow

1972 ◽  
Vol 15 (11) ◽  
pp. 1688-1689
Author(s):  
N. T. Fazullin ◽  
A. B. Isaev
Keyword(s):  
Turbulent Flow ◽  
Hydrodynamic Characteristics

scholarly journals The variation of flow and turbulence across the sediment–water interface

2017 ◽  
Vol 824 ◽  
pp. 413-437 ◽  
Author(s):  
J. J. Voermans ◽  
M. Ghisalberti ◽  
G. N. Ivey
Keyword(s):  
Shear Stress ◽  
Turbulent Flow ◽  
Fluid Shear Stress ◽  
Measurement Techniques ◽  
Hydrodynamic Characteristics ◽  
Transitional Region ◽  
Fluid Viscosity ◽  
Water Interface ◽  
Mean Flow ◽  
The Mean

A basic framework characterising the interaction between aquatic flows and permeable sediment beds is presented here. Through the permeability Reynolds number ($Re_{K}=\sqrt{K}u_{\ast }/\unicode[STIX]{x1D708}$, where$K$is the sediment permeability,$u_{\ast }$is the shear velocity and$\unicode[STIX]{x1D708}$is the fluid viscosity), the framework unifies two classical flow typologies, namely impermeable boundary layer flows ($Re_{K}\ll 1$) and highly permeable canopy flows ($Re_{K}\gg 1$). Within this range, the sediment–water interface (SWI) is identified as a transitional region, with$Re_{K}$in aquatic systems typically$O(0.001{-}10)$. As the sediments obstruct conventional measurement techniques, experimental observations of interfacial hydrodynamics remain extremely rare. The use of refractive index matching here allows measurement of the mean and turbulent flow across the SWI and thus direct validation of the proposed framework. This study demonstrates a strong relationship between the structure of the mean and turbulent flow at the SWI and$Re_{K}$. Hydrodynamic characteristics, such as the interfacial turbulent shear stress, velocity, turbulence intensities and turbulence anisotropy tend towards those observed in flows over impermeable boundaries as$Re_{K}\rightarrow 0$and towards those seen in flows over highly permeable boundaries as$Re_{K}\rightarrow \infty$. A value of$Re_{K}\approx 1{-}2$is seen to be an important threshold, above which the turbulent stress starts to dominate the fluid shear stress at the SWI, the penetration depths of turbulence and the mean flow into the sediment bed are comparable and similarity relationships developed for highly permeable boundaries hold. These results are used to provide a new perspective on the development of interfacial transport models at the SWI.

An Introduction to Turbulent Flow

2000 ◽  
Author(s):  
Jean Mathieu ◽  
Julian Scott
Keyword(s):  
Turbulent Flow
Sign in / Sign up

Export Citation Format

Share Document