scholarly journals METHOD OF CALCULATING THE LIFT COEFFICIENT FOR A WIG’S COMPOUND WING FLYING CLOSE TO THE GROUND

2020 ◽  
pp. 51-61
Author(s):  
Andrey N. Luchkov ◽  
Evgeny V. Zhuravlev ◽  
Egor Y. Cheban
Keyword(s):  
Lift Coefficient ◽  
Calculated Data ◽  
Superposition Method ◽  
Preliminary Design ◽  
Safe Operation ◽  
Method Of Calculation ◽  
Profile Characteristics ◽  
Experimental Values ◽  
Center Section

In the design and characteristics justification of WIG crafts, determination of optimal aerodynamic and moment coefficients and their ratio is still one of the most important problems. Values and ratios of these coefficients provide not only technical tasks performance, but also safe operation of a WIG craft within the framework of AP standards and rules of water transport operation. The paper is devoted to the method of calculating the Cy lift coefficient for the complex compound wing with washers by using the superposition method and verification of calculated data with experimental values. The study was based on TsAGI-876 wing profile characteristics at various relative flight heights.Calculation of the aerodynamic Cy coefficient is performed in several stages:1. Calculation of the aerodynamic Cy coefficient for the center section;2. Calculation of aerodynamic Cy coefficient for the console section;3. Calculation of the total Cy coefficient by using the superposition method.The proposed method of calculation provides an accuracy of up to 93%, which can be considered a satisfactory result for preliminary design of types «B» and «C» WIG crafts.

Analysis of Stress Concentrations in Thick Cylinders With Sideholes and Crossholes

1972 ◽  
Vol 94 (3) ◽  
pp. 815-824 ◽  
Author(s):  
J. C. Gerdeen
Keyword(s):  
Stress Concentration ◽  
Stress Concentrations ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Experimental Values ◽  
Pressure Stress ◽  
Shrink Fit ◽  
Outside Diameter ◽  
Theoretical Results

An approximate theoretical analysis is presented for the determination of stress concentration factors in thick walled cylinders with sideholes and crossholes. The cylinders are subjected to both internal pressure and external shrink-fit pressure. Stress concentration factors are plotted as functions of the geometrical ratios of outside diameter-to-bore diameter, and bore diameter-to-sidehole diameter. Theoretical results are compared to experimental values available in the literature and results of experiments described in a separate paper.

Temperature Preference and Avoidance Responses of the Crayfish, Orconectes obscurus, and Associated Statistical Problems

1982 ◽  
Vol 39 (4) ◽  
pp. 548-553 ◽  
Author(s):  
Dilip Mathur ◽  
Robert M. Schutsky ◽  
Edmund J. Purdy Jr.
Keyword(s):  
Acclimation Temperature ◽  
Published Data ◽  
Temperature Preference ◽  
Preferred Temperature ◽  
Field Collection ◽  
Method Of Calculation ◽  
Final Preferred Temperature ◽  
Statistical Problems ◽  
Avoidance Responses

Acute temperature selection and avoidance responses of the crayfish, Orconectes obscurus, acclimated at field collection temperatures of 1.5–26.0 °C and determined in a spatial thermal gradient, were similar to those noted for fishes. Acclimation temperature was positively correlated with the acute preferred and avoided temperatures; both were several degrees higher than the acclimation temperature. A large proportion of the total variance in these data was unexplained. Most variable responses occurred at low acclimation temperatures. The estimated final preferred temperature ranged from 29.8 to 33.9 °C depending upon the method of calculation. Methods of estimating final preferenda from acute tests are considered arbitrary due to statistical problems and the associated high variability. Statistical problems were also noted in the determination of avoidance temperatures of crayfish due to nonindependence of observations on the same organism. No differences were noted (P < 0.05) between the preferred or avoided temperatures when the direction of field temperatures was rising or falling. A statistical comparison of the new and published data on this species revealed general similarities, particularly over an acclimation temperature range of 18.0–30.0 °C. The analysis minimizes the importance of site-specific studies on this species using the current acute testing methods.Key words: crayfish, temperature preference, avoidance, populational variation, statistics, experimental and statistical problems

scholarly journals Dynamic Impact Factor Determination of an Existing Pre-stressed Concrete I-Girder Bridge Using Vehicle-Bridge Interaction Modelling

2021 ◽  
Vol 10 (3) ◽  
pp. 163-176
Author(s):  
Shuvrodeb Adhikary ◽  
Shohel Rana ◽  
Jerin Tasnim ◽  
Nazrul Islam
Keyword(s):  
Impact Factor ◽  
Dynamic Model ◽  
Superposition Method ◽  
Dynamic Impact ◽  
Mode Superposition Method ◽  
Road Roughness ◽  
Girder Bridge ◽  
Dynamic Impact Factor ◽  
Interaction Problem

The dynamic Impact Factor (IM) of a bridge is influenced by many factors, including Vehicle-Bridge Interaction (VBI), vehicle speed and road roughness. This paper represents the dynamic effects of moving vehicles and the determination of IM of an existing Pre-stressed concrete I-girder bridge utilizing VBI modeling. Evaluation of the IM is expected to provide valuable information for condition assessment and management of the existing bridge. The interaction problem between the vehicle and the bridge includes a dynamic model for the bridge structure subsystem, a dynamic model for the vehicle subsystem, interaction constraints, road roughness modelling and numerical solution techniques for the dynamic systems. The Half-car model is utilized for modelling of the vehicle dynamics and the bridge dynamic model is idealized according to Finite Element Method (FEM). Then FEM along with the mode superposition method are utilized for determining the Equation of Motion (EOM) for the bridge subsystem. D’Alembert’s principle is used for developing EOM for the vehicle subsystem. The interaction between vehicle vibration and bridge vibration is established through the contact forces between the wheels and the bridge by employing the compatibility relationship between the contact points and by applying the static equilibrium condition. Lastly, Newmark’s-β method is used for solving the coupled mathematical model of the vehicle and bridge interaction problem to determine the responses of the two sub-systems. The whole procedure is then performed for different vehicle speeds and various bridge deck surface roughness conditions to determine the dynamic impact on the existing I-girder bridge named Teesta Bridge located in Bangladesh.

Calcul des éléments dipolaires et quadrupolaires de la matrice de transition moléculaire dans Na2

1990 ◽  
Vol 68 (4-5) ◽  
pp. 365-368 ◽  
Author(s):  
K. Hussein ◽  
O. Babaky
Keyword(s):  
Numerical Integration ◽  
Electronic States ◽  
Transition Elements ◽  
Simple Method ◽  
Selection Rules ◽  
Variable Formula ◽  
Method Of Calculation ◽  
Analytical Integration ◽  
Fifth Order

In this paper, we study a calculation of the transition elements [Formula: see text] between electronic states of the diatomic molecules Na2. We show the necessary selection rules for the determination of these operators by a method of analytical integration on the variable [Formula: see text], combined with a numerical integration to fifth order. The values found by this simple method of calculation are very reasonable and show that the important transitions [Formula: see text], [Formula: see text]; and [Formula: see text] of the dimer Na2 are dipolar. [Traduit par la revue]

EVALUATION OF THE STRESSED DEFORMED STATE OF MAIN GAS PIPELINES RUNNING IN PERMANENTLY FROZEN GROUNDS

2020 ◽  
pp. 58-63
Author(s):  
M. M. Sidorov ◽  
N. I. Golikov ◽  
R. P. Tihonov
Keyword(s):  
Experimental Data ◽  
Calculated Data ◽  
Gas Pipeline ◽  
Loss Of Stability ◽  
Portable Equipment ◽  
Ray Method ◽  
X Ray ◽  
Deformed State ◽  
Pipeline Monitoring

The work evaluates the stress deformed state of the section of the interfield gas collecting main, running in permanently frozen grounds. The object of research is a section of a pipeline with an arched discharge formed as a result of loss of stability as a result of thermal erosion of permanently frozen grounds to disturbance of the vegetation cover. The determination of stresses was carried out by the X-ray method using portable equipment. The experimental data were analyzed with the calculated. The calculated data were obtained by measuring the spatial position of the gas pipeline section. The obtained values of the acting stresses and the estimates of the critical indicators of the gas pipeline monitoring section made it possible to reasonably estimate the stress state. The methodology for determining the acting stresses of pipelines using portable X-ray equipment can be successfully applied to estimate the stressed-deformed state of pipeline systems running in the zone of permafrost.

Robust Concurrent Concept Selection and System Synthesis

1994 ◽  
Author(s):  
Wei Chen ◽  
Janet K. Allen ◽  
Farrokh Mistree
Keyword(s):  
Irrigation System ◽  
Preliminary Design ◽  
Continuous Variables ◽  
Engineering Systems ◽  
Concept Selection ◽  
Complex Engineering ◽  
Solar Powered ◽  
System Variables ◽  
Complex Engineering Systems

Abstract In this paper, we introduce a concurrent approach to preliminary system design by using a modification of Taguchi’s method of robust design. It is possible to model interactions among component concept selections and synthesis of system variables. This approach also can improve computational efficiency and provide more design knowledge for the conceptual design of complex engineering systems. This technique is effective in dealing with both discrete and continuous variables simultaneously in design. We illustrate our approach by the preliminary design of a solar powered irrigation system. The selections of critical component concepts are integrated with the determination of system variables, i.e., the thermodynamic operating parameters.

scholarly journals Development of a three-parameter model of the shoe brake contact interaction with the drum in mine hoisting machine

2018 ◽  
Vol 60 ◽  
pp. 00039
Author(s):  
Kostiantyn Zabolotnyi ◽  
Oleksand Zhupiiev ◽  
Artur Molodchenko
Keyword(s):  
Contact Interaction ◽  
Accurate Determination ◽  
Mining Industry ◽  
Flexural Stiffness ◽  
Safe Operation ◽  
Translational Movement ◽  
Longitudinal Stiffness ◽  
The Coefficient Of Friction ◽  
Maximum Contact

For safe operation of mine hoisting machines (MHM) in the mining industry, it is necessary to provide high constructive reliability of brake systems, in particular, brake systems based on the block brake. The contact interaction of the brake with the translational movement of the shoes applied in MHM, remains insufficiently studied. In particular, it is necessary to develop a technique for accurate determination of the braking moment and forces in the elements of the brake linkage, as well as to study the nature of the pressure distribution along the brake beam. The purpose of this article is to simulate the contact interaction of the MHM brake taking into account the coefficient of friction, the ratio of the flexural stiffness to the longitudinal stiffness of a beam, as well as the ratio of the transverse stiffness of a lining to the flexural stiffness of a beam. The application of the developed model will help to reduce the maximum contact pressure in the shoe brakes of the mine hoisting machines and will allow more accurate calculation of the braking moment value compared to existing methods.

Experimental analysis of cell pattern on grid fin aerodynamics in subsonic flow

2019 ◽  
Vol 234 (3) ◽  
pp. 537-562
Author(s):  
Manish Tripathi ◽  
Mahesh M Sucheendran ◽  
Ajay Misra
Keyword(s):  
Subsonic Flow ◽  
Lift Coefficient ◽  
Aerodynamic Performance ◽  
Aerodynamic Efficiency ◽  
Grid Fin ◽  
Stall Angle ◽  
The Individual ◽  
The Impact ◽  
Control Surfaces

Grid fins consisting of a lattice of high aspect ratio planar members encompassed by an outer frame are unconventional control surfaces used on numerous missiles and bombs due to their enhanced lifting characteristics at high angles of attack and across wider Mach number regimes. The current paper accomplishes and compares the effect of different grid fin patterns on subsonic flow aerodynamics of grid fins by virtue of the determination of their respective aerodynamic forces. Furthermore, this study deliberates the impact of gap variation on aerodynamics of different patterns. Results enunciate enhanced aerodynamic efficiency, and lift slope for web-fin cells and single diamond patterns compared to the baseline model. Moreover, the study indicates improved aerodynamic performance for diamond patterns with higher gaps by providing elevated maximum lift coefficient, delayed stall angle, and comparable drag at lower angles. The study established the presence of an additional effect termed as the inclination effect alongside the cascade effect leading to deviations with respect to lift, stall, and aerodynamic efficiency amongst different gap variants of the individual patterns. Thus, optimization based on the aerodynamic efficiency, stall angle requirements, and construction cost by optimum pattern and gap selection can be carried out through this analysis, which can lead to elevated aerodynamic performance for grid fins.

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