Correction of Local Collection Efficiency Based on Roughness Element Concept for Glaze Ice Simulation

2020 ◽  
Vol 36 (5) ◽  
pp. 607-622
Author(s):  
Taekeun Yoon ◽  
Kwanjung Yee
Keyword(s):  
Contact Angle ◽  
Load Distribution ◽  
Physical State ◽  
Collection Efficiency ◽  
Roughness Element ◽  
Aerodynamic Performance ◽  
The State ◽  
Proposed Model ◽  
Roughness Elements ◽  
Ice Conditions

ABSTRACTIn glaze ice conditions, beads on the surface usually grow to form roughness elements through coalescence, finally resulting in enhancement of local collection efficiency. However, the effects of roughness elements due to freezing of beads are not reflected on the local collection efficiency in CFD icing simulations. This is problematic for predicting the resultant ice shape, which may lead to inaccurate aerodynamic performance and load distribution. The aim of this study is to propose a macroscopic icing model which can reflect bead microscopic phenomena using the Eulerian approach. To this end, a correction was made for collection efficiency by introducing a novel parameter - the effective impinging angle- which is the angle to calculate the local collection efficiency depending on the physical state of surface. It is assumed that the parameter related to the contact angle represents the state of beads. The computational icing analysis of airfoil was performed using the proposed model both in the rime condition and glaze conditions. The results show that the icing characteristics in the feather region is captured with enhanced accuracy in both conditions.

scholarly journals Trajectory Estimation of Hypersonic Glide Vehicle Based on Analysis of Aerodynamic Performance

2019 ◽  
Vol 37 (6) ◽  
pp. 1102-1110
Author(s):  
Yunpeng Cheng ◽  
Xiaodong Yan ◽  
Feng Cheng
Keyword(s):  
High Speed ◽  
Engineering Calculation ◽  
Aerodynamic Performance ◽  
The State ◽  
Aerodynamic Parameter ◽  
Trajectory Estimation ◽  
Aerodynamic Model ◽  
Proposed Model ◽  
Improve Accuracy ◽  
Nonlinear Aerodynamic

Due to high speed and high maneuverability of hypersonic glide vehicles (HGVs), the state estimation of such targets has always been a research hotspot. In order to improve accuracy of the trajectory estimation, a nonlinear aerodynamic parameter model for target estimation based on aerodynamic performance analysis is proposed. Firstly, the dynamic characteristics of the hypersonic glide vehicle during the hypersonic gliding stage was analyzed. Then, aiming at HTV-2-liked vehicle, the engineering calculation method was used to form the reference aerodynamic model for the target estimation. Secondly, a deviation model described by first-order Markov process was introduced to compensate the uncertainties of the unknown maneuver information from the target. Finally, extended Kalman filter was utilized to estimate the state of the target. The simulation results show that the proposed model is able to improve the accuracy of acceleration estimation for the HTV-2-liked hypersonic gliding vehicles.

Static roughness element effects on protuberance full-span wing at micro aerial vehicle application

2021 ◽  
pp. 095441002110499
Author(s):  
Hossein Jabbari ◽  
Mohammad Hassan Djavareshkian ◽  
Ali Esmaeili
Keyword(s):  
Reynolds Number ◽  
Flow Control ◽  
Vortex Shedding ◽  
Separation Bubble ◽  
Roughness Element ◽  
Aerodynamic Performance ◽  
Turbulence Structure ◽  
Laminar Separation Bubble ◽  
Laminar Separation ◽  
Roughness Elements

Although the tubercle wings provide good maneuverability at post-stall conditions, the aerodynamic performance at pre-stall angles is threatened by forming a laminar separation bubble at the trough section of the tubercle wing; consequently, the flight endurance and range are reduced. In the present study, the idea of passive flow control is introduced by using the distribution of static roughness elements on a full-span wing with a sinusoidal leading edge. Initially, the effect of roughness element length, height, and its location are studied at a pre-stall angle (16-degree). Their effect on the laminar separation bubble and vortex shedding formed behind the wing are also investigated. The Reynolds number is assumed to be equal to [Formula: see text] which is in the range of critical Reynolds number and matches to the micro aerial vehicles application. An improved hybrid model, improved delay detached eddy simulation IDDES, has been used to model the flow turbulence structure. In the extended transition region at low Reynolds numbers, the roughness bypassed the instability. Consequently, roughening the surface of the aerofoil increased the boundary layer’s flow momentum, making it more resistible to adverse pressure gradients. By suppressing the bubble, the static roughness element led to pre-stall flow control, which saw an increase in lift coefficient, [Formula: see text], and a decrease in drag coefficient, [Formula: see text]. The results have been demonstrated that the aerodynamic performance, [Formula: see text], has been improved approximately 22.7%, 38%, and 45% for [Formula: see text], and [Formula: see text], respectively. The optimal arrangement of static roughness elements could decline the size of the vortices and strengthen the cores associated with them. This claim can be interpreted with the vortex shedding frequency.

scholarly journals Spatial regression methods to evaluate beekeeping production in the state of Rio de Janeiro

2013 ◽  
Vol 65 (2) ◽  
pp. 553-558
Author(s):  
W.S. Tassinari ◽  
M.C. Lorenzon ◽  
E.L. Peixoto
Keyword(s):  
Rio De Janeiro ◽  
High Performance ◽  
Spatial Regression ◽  
The State ◽  
Spatial Effects ◽  
Regression Methods ◽  
Honey Production ◽  
Production Factors ◽  
Proposed Model ◽  
Wild Vegetation

Brazilian beekeeping has been developed from the africanization of the honeybees and its high performance launches Brazil as one of the world´s largest honey producer. The Southeastern region has an expressive position in this market (45%), but the state of Rio de Janeiro is the smallest producer, despite presenting large areas of wild vegetation for honey production. In order to analyze the honey productivity in the state of Rio de Janeiro, this research used classic and spatial regression approaches. The data used in this study comprised the responses regarding beekeeping from 1418 beekeepers distributed throughout 72 counties of this state. The best statistical fit was a semiparametric spatial model. The proposed model could be used to estimate the annual honey yield per hive in regions and to detect production factors more related to beekeeping. Honey productivity was associated with the number of hives, wild swarm collection and losses in the apiaries. This paper highlights that the beekeeping sector needs support and help to elucidate the problems plaguing beekeepers, and the inclusion of spatial effects in the regression models is a useful tool in geographical data.

An Experimental Investigation of Structured Roughness Effect on Heat Transfer During Single-Phase Liquid Flow at Microscale

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Ting-Yu Lin ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Enhancement Factor ◽  
Roughness Element ◽  
Hydraulic Diameter ◽  
Transfer Enhancement ◽  
Roughness Elements ◽  
The Heat Transfer Coefficient

The effect of structured roughness on the heat transfer of water flowing through minichannels was experimentally investigated in this study. The test channels were formed by two 12.7 mm wide × 94.6 mm long stainless steel strips. Eight structured roughness elements were generated using a wire electrical discharge machining (EDM) process as lateral grooves of sinusoidal profile on the channel walls. The height of the roughness structures ranged from 18 μm to 96 μm, and the pitch was varied from 250 μm to 400 μm. The hydraulic diameter of the rectangular flow channels ranged from 0.71 mm to 1.87 mm, while the constricted hydraulic diameter (obtained by using the narrowest flow gap) ranged from 0.68 mm to 1.76 mm. After accounting for heat losses from the edges and end sections, the heat transfer coefficient for smooth channels was found to be in good agreement with the conventional correlations in the laminar entry region as well as in the laminar fully developed region. All roughness elements were found to enhance the heat transfer. In the ranges of parameters tested, the roughness element pitch was found to have almost no effect, while the heat transfer coefficient was significantly enhanced by increasing the roughness element height. An earlier transition from laminar to turbulent flow was observed with increasing relative roughness (ratio of roughness height to hydraulic diameter). For the roughness element designated as B-1 with a pitch of 250 μm, roughness height of 96 μm and a constricted hydraulic diameter of 690 μm, a maximum heat transfer enhancement of 377% was obtained, while the corresponding friction factor increase was 371% in the laminar fully developed region. Comparing different enhancement techniques reported in the literature, the highest roughness element tested in the present work resulted in the highest thermal performance factor, defined as the ratio of heat transfer enhancement factor (over smooth channels) and the corresponding friction enhancement factor to the power 1/3.

Infrared thermography of hypersonic boundary layer transition induced by isolated roughness elements

2021 ◽  
Author(s):  
Shicheng Liu ◽  
Meng Wang ◽  
Hao Dong ◽  
Tianyu Xia ◽  
Lin Chen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Infrared Thermography ◽  
Roughness Element ◽  
Transition Process ◽  
Boundary Layer Transition ◽  
Hypersonic Boundary Layer ◽  
Layer Transition ◽  
Leading Role ◽  
Roughness Elements ◽  
Element Shape

Roughness element induced hypersonic boundary layer transition on a flat plate is investigated using infrared thermography at Ma = 5 and 6 flow condition. Surface Stanton number is acquired to analyze the effect of roughness element shape and height on the transition process. The correlation between the vortex structure induced by roughness element and the wall heat streaks is established. The results indicate that higher roughness element would induce stronger streamwise heat flux streaks, lead to transition advance in streamwise centerline and increase the width of spanwise wake. Moreover, for low roughness element, the effect of the shape is not obvious, and the height plays a leading role in the transition; for tall roughness element, the effect on accelerating transition for the diamond roughness element is the best, the square is the worst, and the shape plays a leading role in the transition.

Acoustic and phase portrait analysis of leading-edge roughness element on laminar separation bubbles at low Reynolds number flow

2021 ◽  
pp. 095441002110443
Author(s):  
Hossein Jabbari ◽  
Esmaeili Ali ◽  
Mohammad Hasan Djavareshkian
Keyword(s):  
Reynolds Number ◽  
Phase Portrait ◽  
Separation Bubble ◽  
Roughness Element ◽  
Low Reynolds Number ◽  
Leading Edge ◽  
Suction Side ◽  
Laminar Separation ◽  
Roughness Elements ◽  
Edge Roughness

Since laminar separation bubbles are neutrally shaped on the suction side of full-span wings in low Reynolds number flows, a roughness element can be used to improve the performance of micro aerial vehicles. The purpose of this article was to investigate the leading-edge roughness element’s effect and its location on upstream of the laminar separation bubble from phase portrait point of view. Therefore, passive control might have an acoustic side effect, especially when the bubble might burst and increase noise. Consequently, the effect of the leading-edge roughness element features on the bubble’s behavior is considered on the acoustic pressure field and the vortices behind the NASA-LS0417 cross-section. The consequences express that the distribution of roughness in the appropriate dimensions and location could contribute to increasing the performance of the airfoil and the interaction of vortices produced by roughness elements with shear layers on the suction side has increased the sound frequency in the relevant sound pressure level (SPL). The results have demonstrated that vortex shedding frequency was increased in the presence of roughness compared to the smooth airfoil. Also, more complexity of the phase portrait circuits was found, retrieved from velocity gradient limitation. Likewise, the highest SPL is related to the state where the separation bubble phenomenon is on the surface versus placing roughness elements on the leading edge leads to a negative amount of SPL.

ECONOMIC SECURITY MANAGEMENT OF AGRICULTURAL ENTERPRISES AT THE REGION

2019 ◽  
Vol 4 (4) ◽  
pp. 388-394
Author(s):  
Viktoriia Hmyria ◽  
Volodymyr Kucherenko
Keyword(s):  
Agricultural Production ◽  
Economic Security ◽  
The State ◽  
Economic Stability ◽  
National Interests ◽  
Agricultural Enterprises ◽  
Theoretical Approaches ◽  
Proposed Model ◽  
Fixed Assets ◽  
Definition Of

The purpose of this article is to study theoretical approaches to definition of economic essence and directions of economic security formation of agricultural enterprises at the region. Analysis of the theoretical aspects of the research object showed that currently there are different approaches to the economic security interpretation. It is considered as a process of meeting public needs, protection of the state national interests, the economic stability, the state of the national economy, in which the country provides its own sovereignty, a state of protection against a certain type of threats. Certain realities of a market economy require fundamentally new approaches to the formation and increase of efficiency of agrarian enterprises functioning, and thus ensure their economic security. In the context of the latest scientific dimensions, it has been found out that the economic security of agricultural enterprises is a complex of sophisticated branched processes, methods, tools, levers of influence on activity for the purpose of increasing the economic activity efficiency of entities. In this regard, there are many different opinions regarding the components of enterprises economic security. It is proved that the economic security of enterprises is characterized by certain features in the regional context of their formation and application to agricultural production. The proposed model Forsythe technology modernization of a regional mechanism of economic security at agricultural enterprises will allow to determine more efficiently the volume of investments, tax burden on the industry and crediting enterprises, depreciation deductions etc., which will effectively affect the activity of the enterprise, and hence ensure its basic – economic security. Keywords: economic security, agricultural enterprises, natural conditions, fixed assets, information security, financial security.

The Role of Two-Dimensional Roughness Element in the Laminar-Turbulent Process in the Favorable Pressure Gradient of the Swept Wing

2014 ◽  
Vol 9 (4) ◽  
pp. 65-73
Author(s):  
Stepan Tolkachev ◽  
Valeria Kaprilevskaya ◽  
Viktor Kozlov
Keyword(s):  
Liquid Crystal ◽  
Roughness Element ◽  
Frequency Interval ◽  
Two Dimensional ◽  
Swept Wing ◽  
Liquid Crystal Thermography ◽  
Roughness Elements ◽  
Favorable Pressure Gradient ◽  
Turbulent Process

In the article using a liquid crystal thermography investigated the development of stationary and secondary disturbances, which were excited by cylindrical and two-dimensional roughness elements. It was shown, that two-dimensional roughness element has a destabilizing effect on disturbances, induced by cylindrical roughness element. Also the twodimensional roughness element is able to excite the stationary structures, and then the secondary disturbances the frequency interval of which is lower than in the case of stationary vortices excitation by cylindrical roughness element

scholarly journals SEIRS model for virus spreading with time delay

2018 ◽  
Vol 173 ◽  
pp. 02042
Author(s):  
Shi-wei Lu ◽  
Gang Wang ◽  
Tong-rui Chen ◽  
Run-nian Ma
Keyword(s):  
Time Delay ◽  
System Dynamics ◽  
Stable Condition ◽  
The State ◽  
Node Degree ◽  
Hurwitz Stability ◽  
Proposed Model ◽  
Virus Spreading ◽  
Infection Stage

In view of the latent characteristic of virus, the escaped state is considered in the model of virus spreading and employed to describe the state of nodes that are infected but not activated. A novelSusceptible–Escaped–Infected–Removed–Susceptible (SEIRS) model with delay is presented for virus spreading based on the escaped mechanism. In the proposed model, time delay, as an important factor, is considered in the infection stage, as well as the node degree of network. Thereafter, system dynamics equations are derived for the model, and the stable condition of the system is investigated via the criterion of Routh-Hurwitz stability. Finally, simulations are demonstrated to illustrate the proposedmodel and its performance.

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