Chord Ratio Research Articles

Erythrocyte fractionation by velocity sedimentation and discontinuous density gradient centrifugation

Investigation of development, maturation and senescence in fish red blood cells depends on effective separation methods. Preliminary to initiation of studies of this type the erythrocytes of goldfish,Carassius auratus, and rainbow trout,Oncorhynchus mykiss, were fractionated by velocity sedimentation at unit gravity or discontinuous Percoll density gradient centrifugation in an attempt to separate and characterize enriched populations of juvenile and mature cells. Cytomorphological variables were assessed by microphotography (trout) and image analysis (goldfish). In both species velocity sedimentation led to fractions which were readily recognized in terms of mean length (maximum cell chord), area and shape (chord ratio, form factor), and sufficiently enriched for some types of study. Density gradient centrifugation also lead to cell separation. However, fractional densities appeared to reflect nuclear rather than cellular morphologies, and the fractions obtained were not readily categorized in relation to stage of development. Accordingly, at the present time, velocity sedimentation appears to offer the more suitable means for fractionating red cells for investigation of maturation and aging processes.

A Study of Aeroacoustic Performance of a Contra-Rotating Axial Flow Compressor Stage

The paper reports the results of an experimental investigation into the aeroacoustic performance of a contra-rotatingaxial flow compressor stage having a hub-tip ratio of 0.66. Aerodynamic superiority of a contra-stage is examined from the point of view of higher pressure rise, increased through flow and rotating stall suppression. Measurements of sound pressure level and real-time analysis of the noise signals is reported for different speed combinations for clean and distorted inlet flow for two axial gaps between the contra-rotors. The effect of pitch chord ratio and axial gap between the rotors on the aeroacoustic performance is discussed. The study reveals that the axial gap between the rotors significantly affects the aeroacoustic performance of a contra-stage.

Interference Drag of a Turbulent Junction Vortex

The interference drag identified with the junction of a streamlined cylindrical body and a flat plate was investigated. The junction drag was calculated from a set of detailed, self consistent, high quality data using a control volume approach. The drag for the isolated flat plate and streamlined cylinder making up the junction was calculated using boundary-layer solvers together with surface pressure measurements. For the particular and relatively thick body under consideration, the results show a significant increase in drag due to the junction. These and other available results indicate that the interference drag has a systematic dependence on the thickness to chord ratio. The junction vortex wake increases the downstream flat plate drag significantly. Because of this effect, a unique value for the drag force, drag coefficient, or induced drag coefficient for a junction vortex flow would require that the geometry be specified in detail. The induced drag and the total pressure losses identified with the junction are also reported.

Autorotation of rectangular plates

A series of tests have been conducted on the autorotation of plates of rectangular section and thickness to chord ratios of from 0.1 to 1.0. The major difference from previous work was that the plates spanned the full width of the wind tunnel, i.e. the flow was essentially two-dimensional. The results show major differences from predictions of infinite aspect ratio plates inferred from finite aspect ratio tests as given by Iversen (1979). Moreover, they give excellent correlation with the two-dimensional numerical solution of Lugt (1980) for a 10% thick plate. In contrast to previous results which indicate no autorotation for square cylinders (t/c = 1.0), it is found that autorotation is easily achieved. A new result is that tipspeed ratios are found to be independent of thickness ratio, at approximately the Lugt value over the full range of thickness ratios. Drag coefficients are found to be independent of thickness ratio. There appears to be a critical thickness ratio above and below which the lift coefficients are constant, but are of different magnitude.

Static stability and control characteristics of scissor wing configurations

A scissor wing geometry is introduced as an alternative to variable sweep and oblique wing designs. It is shown that this configuration offers certain enhancements to the stability and control of the aircraft in addition to aerodynamic advantages associated with sweep. It is shown that a scissor wing configuration can maintain a constant static margin throughout its flight Mach numbers. The dependence of the motion of the aircraft neutral point on the sweep angle is shown to be a function of the chord and span ratios. The control authority is studied and shown not to suffer with changes in the sweep angle. It is also suggested that with the use of wing mounted elevons, additional pitch and attitude control can be obtained over a range of sweep angles.

Impulse turbine with self-pitch-controlled guide vanes for wave power generator. Estimation of performance by model testing.

In order to extract a wave power efficiently in a reciprocating flow, a new version of an impulse air turbine with a self-pitch-controlled guide vane is developed. The basic data of the turbine are obtained by a model testing of a turbine rotor with fixed guide vanes under steady and sinusoidal flow conditions. A series of experiments has been executed to clarify the effects of the rotor pitch to chord ratio, guide vane geometry, rotor geometry, and guide vane configuration on the performance. The results are compared with that of a Well turbine. It is clarified that the impulse turbine with self-pitch-controlled guide vanes is superior to a Wells turbine in efficiency and starting characteristics. Furthermore, a suitable choice of design factors is suggested.

Biplane axial turbine for wave power generator. (Aerodynamic characteristics of noncambered blades).

Experimental investigations directed towards improving the overall characteristics of the turbines for wave power generators are reported. Biplane axial turbines with variable setting angles have been manufactured and tested to investigate the effects of the blade setting angle, gap to chord ratio, solidity and arrangement of biplane rotor on the turbine performance. The results have been compared with those of the air turbine with self-pitch-controlled blades and biplane Wells turbine. A suitable choice of the design factors has been suggested.

Hysteretic characteristics of the biplane wells turbine in a reciprocating flow.

The biplane Wells turbine for a wave power generator has many special merits. However, it has hysteretic characteristics in a reciprocating flow, which results in an inaccurate prediction of the performance in a quasi-steady analysis. In order to clarify the hysteretic characteristics, an experimental investigation has been carried out by the use of a sinusoidal axial flow. The results have shown that hysteresis is less sensitive to the gap to chord ratio and more sensitive to the solidity and arrangement of the biplane rotor. By means of flow visualization, the relation between the hysteretic characteristics and the behavior of a wake has been discussed.

28 取付け角を有する複葉式波力タービンの研究

The biplane axial turbine with setting angle has been manufactured and tested to investigate the effects of setting angle, gap to chord ratio, and arrangement of biplane rotor on the turbine performance. The results have been compared with those of the biplane Wells turbine. A suitable choice of the design factors has been suggested. Next, the hysteretic characteristics has been clarified from the viewpoint of the design method. The hysteresis is more sensitive to the arrangement of biplane rotor and less sensitive to the setting angle and gap to chord ratio. By means of flow visualization, the relation between the overall characteristics and the behavior of wakes has been discussed.

複葉式ウェルズタービンのヒステリシス特性

The biplane Wells turbine for wave power generator has many merits. However it has hysteretic characteristics in a reciprocating flow, where results in the inaccurate prediction of performance in a quasi-steady analysis. In order to clarify the hysteretic characteristics, an experimental investigation has been made by use of a sinusoidal axial flow. The results have shown that hysteresis is less sensitive to the gap to chord ratio and more sensitive to the arrangement of biplane rotor. By means of flow visualization, the relation between the hysteretic characteristics and the behavior of wake has been discussed.

Second order correction in super-cavitating hydrofoil cascade theory by singular perturbation expansion.

Singular perturbation expansion techniques are applied to the flow field of super-cavitating hydrofoil cascade for estimating the characteristics to the second order accuracy. A coupled integral equation with respect to the two kinds of higher order pressure doublet is derived from the boundary conditions in every stage of approximation and also a method for obtaing the cavity and hydrofoil characteristics based on the semi-closed model determined by conservation law of momentum is presented. Second order effects on the characteristics are clarified by some numerical examples and then the second order correction curves are presented in short cavity region for the super-cavitating flat plate hydrofoil of high stagger angle and low pitch chord ratio.

Differentiability and the Arc Chord Ratio

Consider a simple closed rectifiable curve, C, in the plane. For points p and q on C, l(p, q) denotes the smallest positive arc length along C from p to q and d(p, q) denotes the usual Euclidean distance from p to q. Since arc length is measured by a limiting process using inscribed polygonal approximations, we might assume that sufficiently small sides of such polygons closely approximate the length of the part of the curve they subtend. In other words, we might expect that the arc chord ratio, l(p, q)/d(p, q), will be close to 1 when p and q are close to one another. A provocative first example is provided by a square. Although for any fixed p

Differentiability and the Arc Chord Ratio

Differentiability and the Arc Chord Ratio

Aerodynamic design of optimum wind turbines

Based on performance envelopes derived by Wilson et al. 6 at Oregon State University, and on a new aerodynamic theory recently proposed by the author, a design procedure is presented and illustrated for one-, two- or three-bladed horizontal axis, constant chord wind turbines of optimum performance. Following specification of the number of blades, B, the lift coefficient, L, and the lift-to-drag ratio, L D , at the design point, algorithms are developed for finding: (i) the tip-speed ratio, X, at which the optimum power coefficient is developed, (ii) the ratio of blade chord to radius and (iii) the manner in which each blade should be twisted along its axis. Programs are given for implementing the calculations iteratively on a programmable calculator.

Lift/drag ratios and sonic boom intensities of a circular wing

The order of attainable lift/drag ratios of a wing of circular planform with biconvex profile has been estimated based on the linearized supersonic flow theory. For this wing, the ground over pressures due to volume and lift have been computed for different flight Mach numbers, thickness to chord ratios, flight altitudes, and wing loadings. It is noted that the booms due to volume and lift are of comparable magnitude even for high flight altitudes.

振動するフラップをもつ翼の空力特性に及ぼすヒンジ間げきの効果

Nonsteady load distributions are investigated on a thin airfoil having oscillating flap, when there is a narrow hinge gap, in an invicid incompressible flow. The angle of attack is assumed to be zero in front of the hinge gap.First the problem is attacked numerically through the POSSIO's integral equation to compare it with the analytical method. The logarithmic singularity in the kernel function is treated with special care. Second the method of matched asymptotic expansion is used to analyze the problem. This brings simple closed expressions.Comparisons of results of the two methods show excellent agreement each other, when the gap width to chord ratio is less than 0.1, say. In appendix, a simplified method is presented where no inner solution needs to be considered; it is useful for gap/chord ratio less than 0.01.

Patterns of Limiting Similarity in Tropical Forest Tiger Beetles (Coleoptera: Cicindelidae)

Patterns of Limiting Similarity in Tropical Forest Tiger Beetles (Coleoptera: Cicindelidae)

Aerodynamic Interference Effects on Oscillating Airfoils with Controls in Ventilated Wind Tunnels

Lift interference effects are discussed based on Bland's integral equation. A mathematical existence theory is utilized for which convergence of the numerical method has been proved for general (square-integrable) downwashes. Airloads are computed using orthogonal airfoil polynomial pairs in conjunction with a collocation method which is numerically equivalent to Galerkin's method and complex least squares. Convergence exhibits exponentially decreasing error with the number n of collocation points for smooth downwashes, whereas errors are proportional to l/n for discontinuous downwashes. The latter is reduced to l//i m+/ with /nth order extrapolation to the limit (using m-1 we obtain hundredfold error reductions with only a 13 % increase of computer time). Numerical results are presented showing acoustic resonance, and the effect of Mach number, ventilation, height to chord ratio, and mode shape on wind tunnel interference. Excellent agreement with experiment is obtained in steady flow, and good agreement is obtained for unsteady flow.

Fine structure of airfoil tone frequency

A method is described for calculating frequency of tone noise radiated by constant‐chord airfoils in uniform low‐turbulence flow. This noise mechanism is important for small aircraft propellers and helicopter rotors, and for automotive radiator cooling fans. Tones are attributed to a feedback loop between instability waves convected downstream within a laminar boundary layer extending to the trailing edge and sound waves generated at the trailing edge and radiated upstream in the inviscid flow. The upstream extent of the feedback path is the most forward distance at which a laminar fluctuation at the tone frequency is unstable. For small increases of flow velocity, the total number of phase cycles around the feedback loop remains constant and the frequency increases less rapidly than flow velocity, When frequency has increased such that the ratio of chord to half the acoustic wavelength becomes an integer, the number of phase cycles abruptly increases to the largest integer for Which a large‐amplitude feedback cycle can occur. The resulting calculated steplike jumps of tone frequency generally match the available data.

Two-Dimensional Compressor Cascades With Optimum Velocity Distribution Over the Blade

Results are presented of a research on an optimum cascade problem in two-dimensional subsonic flow at SVUSS (National Research Institute for Machine Design, Bechovice). The optimisation is based on a determination of the optimum velocity distribution (OVD) and on the solution of the inverse cascade problem. The OVD has been ascertained from a variational problem formulated by Sˇpacˇek as follows: to find such a velocity distribution on the suction surface for which the momentum thickness at the trailing edge has a minimum value. The problem was solved by Ru˚zˇicˇka using a simplified boundary layer method. Inverse cascade problem due to Pola´sˇek was employed to calculate the cascade geometry for a given optimum velocity distribution and the given stagger angle and the space chord ratio. Series of compressor cascades having the optimum velocity distributions has been designed by means of a digital computer. Some cascades of the series were tested in the low-speed windtunnel as well as at the high subsonic speeds. Reasonable agreement between the predicted and the experimental pressure distributions, flow deflection and loss coefficient has been achieved.