Fred E. C. Culick

Bio: Fred E. C. Culick is an academic researcher from California Institute of Technology. The author has contributed to research in topics: Combustion & Nonlinear system. The author has an hindex of 40, co-authored 156 publications receiving 5386 citations. Previous affiliations of Fred E. C. Culick include Massachusetts Institute of Technology.

Comments on a Ruptured Soap Film

Abstract: Subsequent to puncturing at a point, a horizontal soap film develops a hole whose edge, owing to surface tension, propagates outward from the point of puncture at apparently constant velocity. Measurements by Ranz [1] yielded results roughly 10% lower than those calculated on the basis of a simple energy conservation suggested by Rayleigh [2]. The discrepancy was attributed to an additional retarding viscous stress not included in the analysis. It appears, however, that the energy balance quoted [1] neglects an important contribution, indeed related to th viscous effect noted by Ranz, but which reduces the calculated values to 20% below those measured. A more detailed analysis of the motion of the edge gives this result; the neglected contribution arises from inelastic acceleration of the undisturbed fluid up to the velocity of the edge. The concomitant loss in mechanical energy may be identified with viscous dissipation which is estimated to be confined to a relatively thin region. Lack of agreement between calculated and measured values of the edge velocity seems to be causes by a second-order effect in the method used [1] to determine the thickness of the film.

Rotational axisymmetric mean flow and damping of acoustic waves in asolid propellant rocket.

Abstract: .!LTHOUGH for many purposes the one-dimensional apft proximation to the steady flow in a rocket chamber is adequate, there are occasions when more precise information is required. For example, analysis of the stability of pressure oscillations involves knowledge of the streamlines. It has been common practice to use the solution for potential flow subject to the boundary conditions of no flow through the head end and uniform speed normal to the burning surface. Since the Mach number generally is very small, one may assume the density to be constant; the result for the Mach number in a cylindrical chamber is

A review of calculations for unsteady burning of a solid propellant.

Abstract: A = E(l T^ admittance function, Eq. (1) sensitivity of gas phase to pressure changes specific heats of solid and gas activation energy for surface reaction E = ES/RTS enthalpy latent heat for surface reaction; Hp > 0 for exothermic s_urface reaction H = Hp/cT average mass flux fluctuation of mass flux at the surface index in the linear burning rate law, r = ap index in the surface pyrolysis law, Eq. (25) average heat release (per unit volume) in solid heat release in gas phase fluctuations of heat transfer at the average position of the surface, x = 0 fluctuations of heat release at the burning surface linear burning rate universal gas constant initial temperature of propellant, x -*• — co temperature of burning surface flame temperature average chamber temperature, x -*+ °° surface displacement, velocity functions defined in Eqs. (22) and (27) functions defined in Eqs. (22) and (27) stands for p'/p Eqs. (17-20) thermal conductivities of solid and gas stands for (ms'/m)r density of solid propellant and gas phase average density in chamber normalized temperature or a time lag dimensionless frequency parameters for the solid and gas phases; Eqs. (18) and following Eq. (34) real angular frequency mean value fluctuating value evaluated at the solid-gas interface evaluated on the gas (+) or solid ( — ) side evaluated on the gas or solid side of the mean position of the burning surface evaluated at the flame, or just downstream of the flame real part imaginary part

Overview of Combustion Instabilities in Liquid-Propellant Rocket Engines

Abstract: C OMBUSTION instabilities were discovered in solidand liquid-propellant rocket engines at about the same time in the late 1930s. Since then, unstable oscillations have occurred in most, if not practically all, new development programs. Indeed, because of the high density of energy release in a volume having relatively low losses, conditions normally favor excitation and sustenance of oscillations in any combustion chamber intended for a propulsion system. Figure 1 is an abbreviated chronology of some major events and features of the subject during the past 50 years. In one form or another, combustion instabilities have been under continuous study during all of that period. In time, however, the emphasis naturally has shifted, depending on what sort of full-scale systems experienced difficulties. During World War II in the United States, it seems that virtually all work in this subject was concerned with elimination of high-frequency resonant burning (the term used at the time) in small tactical solid rocket motors. The common treatment was usually a form of passive control, involving installation of baffles, resonance rods, or some other modification of geometry. Since then, the need to solve problems of instabilities in solid rockets has continued for motors of all sizes. Much of the basic understanding that has been gained is applicable to liquid rockets, despite the obvious differences in the systems. Although work on combustion instabilities in liquid rockets began in the early 1940s, significant progress was neither achieved nor required until after World War II with the development of large intercontinental ballistic missiles (ICBMs). During the 1960s, the needs of the Apollo program motivated a large amount of work on instabilities, rendered particularly important because of the astronauts

Nonlinear behavior of acoustic waves in combustion chambers

Abstract: This paper is concerned with the general problem of the nonlinear growth and limiting amplitude of acoustic waves in a combustion chamber. The analysis is intended to provide a formal framework within which practical problems can be treated with a minimum of effort and expense. There are broadly three parts. First, the general conservation equations are expanded in two small parameters, one characterizing the mean flow field and one measuring the amplitude of oscillations, and then combined to yield a nonlinear inhomogeneous wave equation. Second, the unsteady pressure and velocity fields are expressed as syntheses of the normal modes of the chamber, but with unknown time-varying amplitudes. This procedure yields a representation of a general unsteady field as a system of coupled nonlinear oscillators. Finally, the system of nonlinear equations is treated by the method of averaging to produce a set of coupled nonlinear first order differential equations for the amplitudes and phases of the modes. These must be solved numerically, but results can be obtained quite inexpensively. Subject to the approximations used, the analysis is applicable to any combustion chamber. The most interesting applications are probably to solid rockets, liquid rockets, or thrust augmentors on jet engines. The discussion of this report is oriented towards solid propellant rockets.

Flight Stability and Automatic Control

Abstract: 1Introduction 2 Static Stability and Control 3 Aircraft Equations of Motion 4 Longitudinal Motion (Stick Fixed) 5 Lateral Motion (Stick Fixed) 6 Aircraft Response to Control on Atmospheric Inputs 7 Automatic Control Theory-The Classical Approach 8 Application of Classic Control Theory to Aircraft Autopilot Design 9 Modern Control Theory 10 Applications of Modern Control Theory to Aircraft Autopilot Design Appendixes A Atmospheric Tables B Geometric, Mass, and Aerodynamic Characteristics of Selected Airplanes C Mathematical Review of Laplace Transforms and Matrix Algebra D Review of Control System Analysis Techniques

Non-sticking drops

Abstract: While the behaviour of large amounts of liquid is dictated by gravity, surface forces become dominant at small scales. They have for example the remarkable ability to make droplets stick to their substrates (even if they are inclined), which is a practical issue in many cases (windshields, window panes, greenhouses, or microfluidic devices). Here we describe how this problem can be overcome with super-hydrophobic materials. These materials are often developed thanks to micro-textures, which decorate a solid surface, and we describe the way such textures modify the wettability of that solid. We conclude by showing the unusual dynamics of drops in a super-hydrophobic situation.

Reducing the contact time of a bouncing drop

Abstract: Surfaces designed so that drops do not adhere to them but instead bounce off have received substantial attention because of their ability to stay dry, self-clean and resist icing. A drop striking a non-wetting surface of this type will spread out to a maximum diameter and then recoil to such an extent that it completely rebounds and leaves the solid material. The amount of time that the drop is in contact with the solid--the 'contact time'--depends on the inertia and capillarity of the drop, internal dissipation and surface-liquid interactions. And because contact time controls the extent to which mass, momentum and energy are exchanged between drop and surface, it is often advantageous to minimize it. The conventional approach has been to minimize surface-liquid interactions that can lead to contact line pinning; but even in the absence of any surface interactions, drop hydrodynamics imposes a minimum contact time that was conventionally assumed to be attained with axisymmetrically spreading and recoiling drops. Here we demonstrate that it is possible to reduce the contact time below this theoretical limit by using superhydrophobic surfaces with a morphology that redistributes the liquid mass and thereby alters the drop hydrodynamics. We show theoretically and experimentally that this approach allows us to reduce the overall contact time between a bouncing drop and a surface below what was previously thought possible.