Cruciform Baffles Deflectors and Other Suppression Devices

Damping produced by cruciform baffles is described in references 13, 28, and 32. These baffles are located physically in the same manner as stringers, so that for the circular cylinder there is the advantage of damping that is independent of liquid height. Cruciform baffles in spherical tanks (ref. 13) were discussed in the preceding sections of this monograph. Cruciform baffles generally provide only a relatively small amount of damping, except when the tank is nearly empty. In fact, cruciform...

Spheroidal and Toroidal Tanks

Only a small amount of general information has been obtained concerning the damping provided by baffles in spherical, oblate and prolate-spheroidal, toroidal, and other tanks that differ from the circular cylinder. Some test data on baffle effectiveness in specific vehicle tank geometries are available in varying degrees of completeness and accuracy, and are summarized in reference 2. References 13 and 40 present experimental data on damping values for various baffle configurations in spherical...

Positive Expulsion Bags and Diaphragms

Positive-expulsion bags and diaphragms are being increasingly employed as liquid-management devices in control and life-support systems under low-gravity conditions. However, diaphragms and bags have not been used in large propellant tanks typical of launch vehicles. Generally, the damping ratio increases with increasing diaphragm thickness and excitation amplitude and decreasing tank diameter. Peak slosh forces occur at successively higher values of excitation frequency as diaphragm thickness...

Ring Baffles

The design of ring-baffle slosh-suppression systems is based on selecting baffle width, spacing, and depth of top baffle to give the required damping ratio f as a function of liquid level in the tank. For a flat rigid-ring baffle in a cylindrical tank, the damping ratio as a function of baffle depth d should be estimated from Miles' equation (ref 31) where W is the baffle width rj the maximum slosh-wave height at the wall and 5, the damping factor (or logarithmic decrement). The term in...

Introduction

Sloshing is defined as the periodic motion of the free surface of a liquid in a partially filled tank or container. In launch vehicles or spacecraft, sloshing can be induced by tank motions resulting from guidance and control system commands or from changes in vehicle acceleration, such as those occurring when thrust is reduced by engine cutoff or when the vehicle encounters wind shears or gusts. If the liquid is allowed to slosh freely, it can produce forces that cause additional vehicle...

Cruciform Baffles and Other Suppression Devices

Cruciform baffles and suppression devices other than ring baffles are not recommended for general use. Cruciform baffles may, however, be useful in nearly empty tanks, and other specific applications may indicate their desirability, in which case their effectiveness should be verified by experimental measurements. Although studies of the influence of flexible diaphragms on liquid sloshing in spherical tanks show that significant damping of slosh forces could be achieved, such devices are...

Damping Without Slosh Suppression Devices

The slosh damping resulting only from the liquid viscosity in various containers without baffles is significant because wall damping alone may be sufficiently large that suppression devices may not be required or their design may be less critical. Several extensive investigations of viscous damping of liquid oscillations in circular cylindrical tanks refs. 23 to 26 have shown that the damping ratio is given quite closely by a relationship involving the liquid's kinematic viscosity, the tank...

General Background

Several types of slosh-suppression devices have been employed successfully to increase the damping of liquid sloshing induced by vehicle motions, while numerous other types have undergone developmental testing or have been used in other applications, and may be applicable for use in launch vehicles or spacecraft. These devices include rigid-ring baffles of various geometries and orientation , cruciform baffles, deflectors, flexible flat-ring baffles, floating cans also lids and mats ,...

Ring Baffle Design

A rather extensive discussion of the baffle design process is given in reference 43. While the primary interest in this analysis is in the flexible baffle concept, the general process is equally applicable to rigid baffles. This discussion also points out that the underlying basis of the design namely, Miles' equation is empirical to a large extent, and hence some care must be employed in applications. The results obtained for large-size tanks and reported in reference 36 may be useful in...

System Compatibility Liquid Systems

Baffle designs should make provision for liquid drainage during launch and ascent, and for bubble escape in boiling cryogenic propellants. These objectives can be achieved by providing gaps between the baffle and the tank wall, inclined baffles, perforated baffles, or a combination of them. Gap size should be large enough to provide adequate liquid drainage but should not be deleterious to slosh damping. Liquids in large tanks in low-gravity conditions might be displaced away from the drain...

Abramson H.n. The Dynamic Behaviour Of Liquids In Moving Containers Nasa Sp-106 1966

NASA Space Vehicle Design Criteria Structures , NASA SP-8009, 1968. I. Abramson, H.N., ed. The Dynamic Behavior of Liquids in Moving Containers. NASA SP-106, 1966. 3. Bauer, H.F. Theory of the Fluid Oscillations in a Circular Cylindrical Ring Tank Partially Filled With Liquid. NASA TN D-557, 1960. Lawrence, H.R. Wang, C.J. and Reddy, R.B. Variational Solution of Fuel Sloshing Modes. Jet Propulsion, vol. 128, no. 11, Nov. 1958, pp. 729-736. 5. Moiseyev, N.N. and...