scholarly journals Study on resistance characteristics of submarine near water surface

2022 ◽  
Vol 355 ◽  
pp. 01002
Author(s):  
Jiabao Chen ◽  
Bangjun Lv ◽  
Likun Peng ◽  
Bin Huang
Keyword(s):  
Free Surface ◽  
Interference Effect ◽  
Resistance Coefficient ◽  
Calculation Model ◽  
Simulation Software ◽  
Fluid Simulation ◽  
Wave System ◽  
Kelvin Wave ◽  
Friction Resistance ◽  
Pressure Resistance

The submarine is usually affected by free surface and the navigation resistance increases when sailing near the surface. In order to study the specific resistance characteristics of submarine sailing near the surface, the SUBOFF with appendages was taken as the research object, and the calculation model was built based on Star CCM+ fluid simulation software, and the resistance coefficients under different submarine depths and speeds were calculated. Through comparative analysis, the influence of the depth and speed of the submarine on the resistance components was obtained, and the cause of the formation was analyzed. The results show that the influence of the depth of submarine on friction resistance coefficient is small in general. With the increase of the depth of the submarine, the pressure resistance coefficient decreases, and the wave amplitude decreases. The shear wave of Kelvin wave system is more obvious and the effect of scattering is weakened, which is of great significance for the study of submarine concealment. With the increase of speed, friction resistance coefficient decreases, the overall change trend of pressure resistance coefficient is first increased and then decreases. The interference effect between free surface and hull increases first and then decreases at each depth. The wave shape changes and resistance results mutually confirm. The free surface mainly generates waves by interacting with the hull, which affects the resistance characteristics of the submarine. The interference effect is greatly affected by the depth and speed of the submarine.

scholarly journals Computational Fluid Dynamics Study of the Dead Water Problem

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Mehdi Esmaeilpour ◽  
J. Ezequiel Martin ◽  
Pablo M. Carrica
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Free Surface ◽  
Internal Wave ◽  
Resistance Coefficient ◽  
Total Resistance ◽  
Friction Resistance ◽  
Water Problem ◽  
Dead Water ◽  
Ship Speed

The dead water problem, in which under certain conditions a vessel advancing in a stratified fluid experiences a considerable increase in resistance respect to the equivalent case without stratification, was studied using computational fluid dynamics (CFD). The advance of a vessel in presence of a density interface (pycnocline) results in the generation of an internal wave that in the most adverse conditions can increase the total resistance coefficient by almost an order of magnitude. This paper analyses the effects of stratification on total and friction resistance, the near field wake, internal and free surface waves, and resistance dynamics. Some of these effects are reported for the first time, as limitations of previous efforts using potential flow are overcome by the use of a viscous, free surface CFD solver. A range of densimetric Froude numbers from subcritical to supercritical are evaluated changing both the ship speed and pycnocline depth, using as platform the research vessel athena. It was found that the presence of the internal wave causes a favorable pressure gradient, acceleration of the flow in the downstream of the hull, resulting in thinning of the boundary layer and increases of the friction resistance coefficient of up to 30%. The total resistance presents an unstable region that results in a hysteretic behavior, though the characteristic time to establish the speed–resistance curve, dominated by the formation of the internal waves, is very long and unlikely to cause problems in modern ship speed controllers.

Design and simulation research of the double-spin folding mechanism based on a suspended missile

2021 ◽  
pp. 154851292110231
Author(s):  
ZH Yuan ◽  
SY Guo ◽  
SN Zhang ◽  
JQ Zhao ◽  
WJ Lu ◽  
...  
Keyword(s):  
High Reliability ◽  
Lift Coefficient ◽  
Great Influence ◽  
Reference Value ◽  
Aerodynamic Characteristics ◽  
Simulation Software ◽  
Fluid Simulation ◽  
Simulation Research ◽  
Double Spin ◽  
Locking Mechanism

Based on the suspension of a missile using folding rotary wings and airbags, in order to improve the basic parameters and motion characteristics of the rotor during the unfolding process and analyze the aerodynamic characteristics of the entire device in the suspension state, after proposing a scheme of double-spin mechanism, the main folding and unfolding mechanism, initial driving device, rotating driving device, and locking mechanism were designed, and the simulation research is studied by the Automatic Dynamic Analysis of Mechanical System and Ansys Fluent Fluid Simulation software, respectively. The results show that the rotation rate was controlled at 41.8 mm/s, the various motion parameters are reasonable, and the operation process is relatively smooth, with high reliability. The speed and pressure value at the tip of the rotor are higher and the aerodynamic disturbance is obvious, which has a great influence on the aerodynamic performance. The speed and pressure distribution of the surrounding flow field is stable, the lift provided is 46 N, and the lift coefficient is 0.55, which can ensure the long-time suspension state of the missile. This paper puts forward a valuable design idea and has practical reference value for the research of the suspended missile.

The Finite Element Analysis of the Large-Scale Converter Transformer Valve Side of the Electric Field

2013 ◽  
Vol 325-326 ◽  
pp. 476-479 ◽  
Author(s):  
Lin Suo Zeng ◽  
Zhe Wu
Keyword(s):  
Finite Element ◽  
Electric Field ◽  
Large Scale ◽  
Calculation Model ◽  
Simulation Software ◽  
Field Calculation ◽  
Element Analysis ◽  
Ansys Simulation ◽  
The Finite Element Analysis ◽  
Electric Field Calculation

This article is based on finite element theory and use ANSYS simulation software to establish electric field calculation model of converter transformer for a ±800kV and make electric field calculation and analysis for valve winding. Converter transformer valve winding contour distribution of electric field have completed in the AC, DC and polarity reversal voltage.

scholarly journals Analytical Method for Calculating Sustainable Airport Capacity

2020 ◽  
Vol 12 (21) ◽  
pp. 9239
Author(s):  
Paola Di Mascio ◽  
Gregorio Rappoli ◽  
Laura Moretti
Keyword(s):  
Federal Aviation Administration ◽  
Calculation Model ◽  
Simulation Software ◽  
Time Interval ◽  
Fast Time ◽  
Safety Issues ◽  
Airport Capacity ◽  
Maximum Delay ◽  
Critical Issues ◽  
Level 3

Capacity is the attitude of an airport to manage a number of operations in a given time interval within a fixed maximum delay (and under given safety conditions). Capacity studies are commonly carried out on five levels of analysis according to the required detail in order to identify the best option that balances economic, logistic and safety issues. This study focuses on level 3 (i.e., analytical methods) developing a calculation model to assess the runway capacity. The model was calibrated by comparing the outputs of different airport configurations with those provided by the circular of the Federal Aviation Administration Airport Capacity and Delay. The model was well calibrated with maximum differences in the analyzed configurations that stood at 1 or 2 movements/hour. The runway capacity of an international airport was calculated and compared to that of the entire airside, assessed through fast time simulation, in a previous study. The analytical model provides runway capacity slightly higher than that of the entire air system, as it cannot evaluate all the critical issues present in the airport that reduce its maximum theoretical capacity. Therefore, depending on the degree of detail required, you can use the developed model or the simulation software; the use of the latter is possible when the airside infrastructure does not adequately support the runway system or in cases of advanced design level.

scholarly journals Research on the Influence of the Distribution Pattern of Building Clusters in Coastal Areas on Wind Environment -Focused on Busan area in Korea

2021 ◽  
Vol 308 ◽  
pp. 02010
Author(s):  
Yang Huimin ◽  
Zhao Shuwen ◽  
Kim Chulsoo
Keyword(s):  
Thermal Environment ◽  
Simulation Software ◽  
Fluid Simulation ◽  
Wind Environment ◽  
Environment Quality ◽  
Ventilation Efficiency ◽  
Urban Thermal Environment ◽  
The City ◽  
Public Environment

With the development of urbanization, the heat island phenomenon has led to further deterioration of the urban thermal environment, resulting in wind environment differences. To study the thermal environment of the city, this paper takes the Busan area in South Korea as the research object and analyzes the connection between the layout of buildings and the wind environment based on the microscopic wind environment characteristics of the coastal area using CFD air-fluid simulation software and suggests that the monsoon influence brought by the coastal currents should be paid attention to, the layout of wind-oriented building groups should be improved, urban air ducts should be established to enhance the ventilation efficiency, and the wind environment of the urban public environment and buildings should be guaranteed. The wind environment quality of urban public environment and indoor environment should be ensured.

An Experimental Study of the Viscous Resistance of a 0,564-CB Form

1979 ◽  
Vol 23 (02) ◽  
pp. 140-156
Author(s):  
P. N. Joubert ◽  
P. H. Hoffmann
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Skin Friction ◽  
Resistance Coefficient ◽  
Viscous Resistance ◽  
Local Skin ◽  
Friction Resistance ◽  
Local Skin Friction ◽  
The University ◽  
Resistance Coefficients

Wind tunnel tests were performed to determine the viscous resistance and its components for a 0.564-CB model from the BSRA Trawler Series. It was found that the sum of the pressure and skin friction resistance coefficients agreed well with the viscous resistance coefficient determined from drag balance tests. The range of Reynolds number examined was from 1.15 × 106 to 5.17 × 106. The results for the viscous resistance and its components were fitted using least-squares methods to various equations. The results were also compared with the results of previous tests done at the University of Melbourne on models of Lucy Ash-. ton and a 0.80-CB tanker. It was found that the skin friction and viscous resistance coefficients had curves of quite different position and slope. Local skin friction distribution showed noteworthy differences, especially at the stern, with high values at the keel and low values approaching the waterline.

scholarly journals Calculation of the maximum velocity of gravity flow in the pond-clarifier with higher aquatic plants

2020 ◽  
Vol 168 ◽  
pp. 00061
Author(s):  
Yevhen Semenenko ◽  
Tetіana Demchenko ◽  
Artyom Pavlichenko
Keyword(s):  
Free Surface ◽  
Aquatic Plants ◽  
Fluid Velocity ◽  
Maximum Velocity ◽  
Resistance Coefficient ◽  
Gravity Flow ◽  
Recycled Water ◽  
Higher Aquatic Plants ◽  
Two Parameters ◽  
The Given

The analysis of the possible maximum fluid flow rates when using higher aquatic plants for clarification of recycled water in the pondclarifier of the tailing pond has carried out. The study has been performed on the basis of a mathematical model of a plane slow stationary gravity flow of a viscous fluid in two parallel layers. The results of the study made it possible to determine the fluid velocity through a layer of higher aquatic plants floating on a free surface. The maximum possible velocity depending on the layer porosity has been determined. This value is necessary to determine the rational parameters of the process of clarifying technical recycled water from particles of the given hydraulic size, taking into account the pond-clarifier geometric dimensions. It is shown that the velocity in the layer with higher aquatic plants has been determined by the ratio of two parameters of this layer - porosity and dimensionless resistance coefficient. It has been shown that the maximum velocity value coefficient in the layer with plants floating on free surface depends only on porosity of this layer and does not depend on its resistance coefficient.

scholarly journals Analysis of temperature characteristics of ink fluid based on power law model in microchannel

2019 ◽  
Vol 11 (3) ◽  
pp. 168781401983358
Author(s):  
Hongyan Chu ◽  
Xuecong Lin ◽  
Ligang Cai
Keyword(s):  
Heat Transfer ◽  
Viscous Dissipation ◽  
Power Law ◽  
Flow Characteristics ◽  
Simulation Software ◽  
Fluid Simulation ◽  
Fluid Temperature ◽  
Power Law Model ◽  
Feature Size ◽  
Temperature Characteristics

In the offset press, ink flows in the microchannel made of two rotating rollers that are in the state of squeezing and contacting. The ink flow characteristics are not only influenced by the viscous dissipation effect, but also change with the heat transfer. First, by summarizing the common viscosity–shear rate models of non-Newtonian fluid, the power law model was chosen for describing offset ink through rheometer measuring. Combined with the experimental data, the viscosity–temperature relationship of the offset ink was described by the Arrhenius’s law. Then, the temperature characteristics of the offset ink fluid in the microchannel were studied using the fluid simulation software FLUENT. The ink fluid temperature field model considering viscous dissipation and heat transfer was established, and the temperature distributions of the ink fluid inside the microchannel and at the exit and entrance were obtained. The influence of the feature size on the ink temperature was also researched. Finally, the ink temperature and flow characteristics were compared with that under the condition without heat transfer. We got the influence of feature size and heat transfer on the ink temperature characteristics. As the feature size is smaller, the ink temperature increase from the microchannel entrance to the exit, increases first and then decreases, and keeps invariant at last. The heat transfer makes the viscous dissipation weaken relatively and then the ink temperature decreases. In a word, the heat transfer enhances as the feature size decreases. The results provide reference for improving the printing quality of offset press.

scholarly journals Water-Exit Process Modeling and Added-Mass Calculation of the Submarine-Launched Missile

2017 ◽  
Vol 24 (s3) ◽  
pp. 152-164 ◽  
Author(s):  
Jian Yang ◽  
Jinfu Feng ◽  
Yongli Li ◽  
An Liu ◽  
Junhua Hu ◽  
...  
Keyword(s):  
Dynamic Model ◽  
Calculation Method ◽  
Added Mass ◽  
Simulation Software ◽  
Fluid Simulation ◽  
Modeling Process ◽  
Complex Fluid ◽  
Simulated Analysis ◽  
Changing Rate ◽  
Water Exit

Abstract In the process that the submarine-launched missile exits the water, there is the complex fluid solid coupling phenomenon. Therefore, it is difficult to establish the accurate water-exit dynamic model. In the paper, according to the characteristics of the water-exit motion, based on the traditional method of added mass, considering the added mass changing rate, the water-exit dynamic model is established. And with help of the CFX fluid simulation software, a new calculation method of the added mass that is suit for submarine-launched missile is proposed, which can effectively solve the problem of fluid solid coupling in modeling process. Then by the new calculation method, the change law of the added mass in water-exit process of the missile is obtained. In simulated analysis, for the water-exit process of the missile, by comparing the results of the numerical simulation and the calculation of theoretical model, the effectiveness of the new added mass calculation method and the accuracy of the water-exit dynamic model that considers the added mass changing rate are verified.

scholarly journals Numerical simulation of turbulent flow through Schiller’s wavy pipe

2014 ◽  
Vol 761 ◽  
pp. 241-260 ◽  
Author(s):  
G. Daschiel ◽  
V. Krieger ◽  
J. Jovanović ◽  
A. Delgado
Keyword(s):  
Turbulent Flow ◽  
Structural Changes ◽  
Stokes Equations ◽  
Resistance Coefficient ◽  
Navier Stokes ◽  
Cross Sectional ◽  
Navier Stokes Equations ◽  
Flow Through ◽  
Pressure Resistance ◽  
Almost All

AbstractThe development of incompressible turbulent flow through a pipe of wavy cross-section was studied numerically by direct integration of the Navier–Stokes equations. Simulations were performed at Reynolds numbers of $4.5\times 10^{3}$ and $10^{4}$ based on the hydraulic diameter and the bulk velocity. Results for the pressure resistance coefficient ${\it\lambda}$ were found to be in excellent agreement with experimental data of Schiller (Z. Angew. Math. Mech., vol. 3, 1922, pp. 2–13). Of particular interest is the decrease in ${\it\lambda}$ below the level predicted from the Blasius correlation, which fits almost all experimental results for pipes and ducts of complex cross-sectional geometries. Simulation databases were used to evaluate turbulence anisotropy and provide insights into structural changes of turbulence leading to flow relaminarization. Anisotropy-invariant mapping of turbulence confirmed that suppression of turbulence is due to statistical axisymmetry in the turbulent stresses.

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