A universal indicial function for pressure prediction at transonic speeds

1997 ◽  
Author(s):  
David Nixon ◽  
David Nixon
Keyword(s):  
Indicial Function

scholarly journals Identification of Fixed-Wing Micro Aerial Vehicle Aerodynamic Derivatives from Dynamic Water Tunnel Tests

Aerospace ◽  
2020 ◽  
Vol 7 (8) ◽  
pp. 116
Author(s):  
Krzysztof Sibilski ◽  
Mirosław Nowakowski ◽  
Dariusz Rykaczewski ◽  
Paweł Szczepaniak ◽  
Andrzej Żyluk ◽  
...  
Keyword(s):  
Unsteady Aerodynamics ◽  
Linear Functions ◽  
Water Tunnel ◽  
Micro Aerial Vehicle ◽  
Indicial Function ◽  
Reduced Frequency ◽  
Aerodynamic Derivatives ◽  
Aerial Vehicle ◽  
Institute Of Technology ◽  
Derivatives Of

A micro air vehicle (MAV) is a class of miniature unmanned aerial vehicles that has a size restriction and may be autonomous. Fixed-wing MAVs are very attractive for outdoor surveillance missions since they generally offer better payload and endurance capabilities than rotorcraft or flapping-wing vehicles of equal size. This research paper describes the methodology applying indicial function theory and artificial neural networks for identification of aerodynamic derivatives for fixed-wing MAV. The formulation herein proposed extends well- known aerodynamic theories, which are limited to thin aerofoils in incompressible flow, to strake wing planforms. Using results from dynamic water tunnel tests and indicial functions approach allowed to identify MAV aerodynamic derivatives. The experiments were conducted in a water tunnel in the course of dynamic tests of periodic oscillatory motion. The tests program range was set at high angles of attack and a wide scope of reduced frequencies of angular movements. Due to a built-in propeller, the model’s structure test program was repeated for a turned-on propelled drive system. As a result of these studies, unsteady aerodynamics characteristics and aerodynamic derivatives of the micro-aircraft were identified as functions of state parameters. At the Warsaw University of Technology and the Air Force Institute of Technology, a “Bee” fixed wings micro aerial vehicle with an innovative strake-wing outline and a propeller placed in the wing gap was worked. This article is devoted to the problems of identification of aerodynamic derivatives of this micro-aircraft. The result of this research was the identification of the aerodynamic derivatives of the fixed wing MAV “Bee” as non-linear functions of the angle of attack, and reduced frequency. The identification was carried out using the indicial function approach.

Application of indicial function for the flutter analysis of long span suspension bridge during erection

2014 ◽  
Vol 14 (1) ◽  
pp. 185-194 ◽  
Author(s):  
Panot Chobsilprakob ◽  
Ki-Du Kim ◽  
Songsak Suthasupradit ◽  
Anaphat Manovachirasan
Keyword(s):  
Suspension Bridge ◽  
Long Span ◽  
Indicial Function ◽  
Flutter Analysis

Indicial functions of arterial remodeling in response to locally altered blood pressure

1996 ◽  
Vol 270 (4) ◽  
pp. H1323-H1333 ◽  
Author(s):  
S. Q. Liu ◽  
Y. C. Fung
Keyword(s):  
Blood Pressure ◽  
Extracellular Matrices ◽  
Arterial Remodeling ◽  
Cross Sectional ◽  
Indicial Function ◽  
Induced Hypertension ◽  
Altered Blood ◽  
Pressure Changes ◽  
The Relationship ◽  
Identical Change

We investigated the effect of locally altered blood pressure on the remodeling processes of the cells and extracellular matrices of the splenic and ileal arteries and used an indicial function approach to quantitatively analyze the relationship between the altered blood pressure and the remodeling processes. Blood pressure in these arteries was locally modulated by constricting the aorta at a location between the celiac and mesenteric bifurcations, resulting in a higher blood pressure at the splenic arteries then at the ileal arteries, After the pressure changes, the cross-sectional areas and the fractions of the cells and extracellular matrices of the splenic and ileal arteries were examined by electron microscopy at 2, 6, 10, 20, and 30 days. We found that both arteries remodeled, but the splenic arteries (higher blood pressure) remodeled more rapidly and to a larger degree than the ileal arteries (lower pressure compared with the splenic arteries) of the same animal. To verify whether an identical change in the blood pressure at the splenic and ileal arteries leads to the same remodeling process in these arteries, we created another model by constricting the aorta at a location between the mesenteric and renal bifurcations, resulting in hypertension of the same level at both splenic and ileal arteries. We found that the remodeling processes of the cells and matrices were almost identical in the arteries with similar changes in blood pressure. Thus we conclude that the remodeling processes of cells and matrices of the splenic and ileal arteries are dependent on the local blood pressure in aorta constriction-induced hypertension, and the indicial analysis is a useful approach in the description of the relationship between the blood pressure and the arterial remodeling processes.

Expansion of Indicial Function Approximations for 2-D Subsonic Compressible Aerodynamic Loads

2012 ◽  
Author(s):  
T. Farsadi ◽  
J. Javanshir
Keyword(s):  
Time Domain ◽  
Step Function ◽  
Aerodynamic Loads ◽  
Indicial Function ◽  
Starting Point ◽  
Function Approximations ◽  
The Time Domain ◽  
New Generation ◽  
Duhamel’S Integral ◽  
General Time

This article deals with the new generation of proper Mach dependent exponential approximations of the indicial aerodynamic functions toward the aeroelastic formulation of 2-D lifting surface in the subsonic compressible flow. The indicial lift response is a useful starting point in the development of a general time-domain unsteady aerodynamic theory. By definition, an indicial function is the response to a disturbance that is applied instantaneously at time zero and held constant thereafter; that is a disturbance given by a step function. If the indicial response is known, then the unsteady loads to arbitrary changes in angle of attack can be obtained through the superposition of indicial responses using Duhamel’s integral. The indicial functions have been used to modify the circulatory part of the lifting force and pitching moment in unsteady compressible aerodynamic models. The coefficients of the approximation are obtained with an indirect approach by relating numerical results obtained for oscillating airfoil in the frequency domain back into the time domain. compressible and supersonic flight speed regimes. Exponential approximations of the subsonic compressible indicial functions in the existing research works are available only in limited Mach numbers (M = 0.5, 0.6, 0.7, 0.8). In the present study, a novel exponential approximation is developed which represent the coefficients of approximations as functions of Mach number (0.5 < M < 0.8).

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