Edward F. Blick

One-dimensional model of diastolic semilunar valve vibrations productive of heart sounds

Abstract The vibrations of the closed semilunar valves were modeled mathematically. The factors which affect diastolic vibration which were identified in the mathematical model relate to the characteristics of the second heart sound.

Bird Aerodynamic Experiments

The senior author’s research in the area of skin friction reduction by compliant coatings led him to investigate the aerodynamic properties of bird feathers. Three separate experiments performed during the last several years are reported in this paper. The experiments are: (1) relation between the compressive modulus of bird feathers and bird maximum level flight speed (2) the effect of flexible slotted-tip feathers on the wing-wake vorticity and (3) the effect of owl leading edge barbs on lift and drag characteristics of wings.

Golden section search method for determining parameters in Robertson-Stiff non-Newtonian fluid model

Abstract A numerical scheme that seeks a direct evaluation of the three parameters A, B, and C in the Robertson and Stiff model describing the rheological behavior of drilling fluids and cement slurries, is presented. The simple numerical scheme renders the Robertson and Stiff model eassy to use. The importance of this scheme lies in the fact that although the Robertson and Stiff model has been proven to be one of the better rheological models for describing the behavior of drilling fluid and cement slurries, it has found very little application in the drilling industry partly because of the relative difficulty in evaluating the model parameters. This scheme would alleviate this problem. Data from five different fluids have been used to validate the scheme and in each case, a very good match was observed. Apart from the fact that this scheme is simpler and more accurate than the geometric mean/graphical method recommended by Robertson and Stiff, it has a uniqueness which is absent in the use of the graphical method.

The Theory of Skin Friction Reduction by a Compliant Coating in a Turbulent Boundary Layer

The response of a compliant surface to pressure fluctuations is known to modify (sometimes decrease) the skin friction in a turbulent boundary layer. This paper develops the surface response (receptance) of a compliant coating to a pressure perturbation. The compliant coating was assumed to be composed of a thin membrane stretched over a shallow layer of liquid. This type of coating has been used successfully by several experimenters to reduce the skin friction. After the surface response equation was developed, the technique developed by Lin and Ffowcs Williams was utilized to determine the Reynolds stresses induced near the vibrating compliant surface. The technique is generalized to allow for random turbulent pressure fluctuations and surface motion, but it is restricted to two-dimensional surface oscillations. The interesting result is that certain combinations of the properties of the compliant coating may induce a negative Reynolds stress in the layer of fluid adjacent to the coating. This layer of fluid may then be responsible for starving the turbulent eddies of their energy supply and causing a reduction in turbulence intensity and skin friction.

Effect of turbulent blood flow on systolic pressure contour in the ventricles and great vessels: Significance related to anacrotic and bisferious pulses

The effect of turbulent blood flow on the contour of systolic pressure in the left and right ventricles and great vessels was investigated in 64 patients undergoing diagnostic cardiac catheterization. Intracardiac pressure and sound were recorded using a catheter-tip micromanometer. Measurements were made in normal subjects and patients with a variety of disorders including aortic stenosis, hypertrophic obstructive cardiomyopathy, coarctation of the aorta and atrial septal defect. Observations showed a consistent association of the intracardiac murmur, which is indicative of turbulence, with a transient reduction of the centrally recorded systolic pressure. The resultant abnormal systolic pressure contour can be explained on the basis of fluid dynamic considerations related to turbulence.

Work of the heart: a general thermodynamics analysis.

Abstract The equation for the rate of energy consumed by the heart was derived from the general energy equation of thermodynamics. Previous estimates of mechanical efficiency, heat loss, kinetic energy and flow work were shown to be valid. Estimates were made of the “order of magnitude” of those terms normally omitted in cardiac work analysis.

Theories of compliant coating drag reductions

Approximately two decades ago, Kramer1–3 reported skin friction drag reductions of up to 60% for compliant‐walled bodies towed in water. Since Kramer’s initial experiments, many other investigators have delved into this intriguing area. The results have been mixed. Some have reported drag reductions in water and air with compliant coatings while others found no decrease in drag. Most of those who found decreases have reported that these decreases were found when the compliant wall was immersed in a turbulent boundary layer. Kramer originally stated that he felt the drag reduction was perhaps due to retarding the transition from laminar to turbulent flow. Benjamin,4 Boggs and Tokita,5 Landahl,6 Kaplan,7 and Gyorgyfalvy8 were among the early theoreticians who examined the possibilities of retarding transition by compliant walls. Generally, their calculations showed that with the proper compliant wall properties it was theoretically possible to retard transition. A few years later most of the theoretical wor...

Sinus of Valsalva: a converging nozzle that contributes to stable flow in the coronary arteries

The anatomy of the sinuses of Valsalva has not been considered from the viewpoint of a converging nozzle. Converging nozzles reduce turbulence. We reviewed computed tomographic images of the left and right sinuses of Valsalva in 20 consecutive patients. The sinuses of Valsalva were shown to have a shape in the axial projection that approximates a cubic equation nozzle, although the sinuses of Valsalva are not axisymmetric. The ratios of the cross‐sectional area of the inlet to cross‐sectional areas of the outlet, assuming the sinuses are axisymmetric, were 14 and 17 in the left and right sinuses, respectively. Calculations by others show that turbulent kinetic energy at the exit (at the coronary ostia) of such axisymmetric nozzles would be reduced by 97%. We conclude that the sinuses of Valsalva have the configuration of a converging nozzle and prevent or reduce turbulent flow in the proximal portions of the coronary arteries.

EVALUATION OF LOSS OF INTIMAL COMPLIANCE ON RESISTANCE TO FLOW IN THE COMMON CAROTID ARTERY.

Abstract : Much attention has focused in the past on the relationship between resistance to the flow of blood and vascular distensibility. In addition to the importance of vascular distensibility and its influence on internal diameter, flow resistance might also be altered by a compliant effect from the soft intimal lining. This compliant effect could be characterized by an ability of the arterial wall to change in thickness under varying conditions of blood volume and pressure, thus altering the internal geometry of the vessel and possibly damping out velocity fluctuations in the blood. The damping out of these velocity fluctuations would then add to the reduction in flow resistance. Based upon these considerations, we inquired whether a physiological analogy to this compliant-surface effect exists in the wall of an artery. An attempt was made to evaluate the role of the soft intimal lining in providing a more efficient vessel for pulsatile flow, since pathological stiffening of the arterial wall is associated with an increased resistance to flow in man. Pressure drop measurements made on the canine common carotid artery encased in hard plastic indicated no significant difference in resistance to flow between the normal internal lining and the artificially hardened intima. It appears that the compliant-surface effect does not occur during laminar pulsatile flow in large arteries.