AJK2011-33003 CAVITATION FROM A BUTTERFLY VALVE: COMPARING 3D SIMULATIONS TO 3D X-RAY COMPUTED TOMOGRAPHY FLOW VISUALIZATION

ABSTRACT Flow control valves may experience localized cavitation when the local static pressure drops to the liquid vapor pressure. Localized damage to the valve and surrounding area can occur when the vapor cavity collapses. Valve designs that reduce cavitation are based on empirical evidence and accumulated experience, but there are still considerable cavitation problems in industry. Valve designers may use computational fluid dynamics (CFD) to simulate cavitation in flow control valves, but model validation is challenging because there are limited data of local cavitation from the valve surface. Typically, the intensity of cavitation in a control valve is inferred from measurements of observable side effects of cavitation such as valve noise, vibration, or damage to the valve assembly. Such an indirect approach to characterizing cavitation yields little information about the location, degree, and extent of the cavitation flow field that can be used in CFD validation studies. This study uses 3D X-ray computed tomography (CT) imaging to visualize cavitation from a 5.1 cm diameter butterfly valve and compares the resulting vapor cloud to that predicted by CFD simulations. Qualitative comparisons reveal that the resulting cavitation structures are captured by the simulations when a small amount of noncondensable gas is introduced into the fluid and the simulations are completed in a transient mode

The Treatment of the Mentally Ill in Supermax Facilities

As a criminal justice policy, researchers have encountered numerous problems attempting to evaluate whether supermax confinement achieves its desired goals. Among the many goals of supermax confinement is the incapacitation of the “worst of the worst” inmates. This type of custody, however, has been widely criticized for worsening inmate mental health. In an effort to better understand the treatment of the mentally ill in supermax confinement, we performed a content analysis on 42 state correctional policies. We found considerable variation exists regarding the treatment of the mentally ill as prescribed by official policies and that the majority of correctional policies dictate some level of treatment or intervention for supermax inmates. As criticism regarding the indefinite use of lockdown increases, we argue it is important correctional departments have a foundation that protects inmates and the agency itself, which begins with official policies

Taking stock: A Meta-Analysis of the Predictors of Restrictive Housing

Two competing views on the use of restrictive housing have emerged in the literature. The first position has argued that restrictive housing helps make correctional institutions safer and more secure environments, largely by incapacitating violent and dangerous inmates. In contrast, a second perspective has maintained that restrictive housing not only causes serious psychological damage and increases criminal coping, but also that it has served as a mechanism for officials to punish certain groups of inmates unfairly. This study tests these competing hypotheses by meta-analyzing the literature on the predictors of placement in restrictive housing. The results of this investigation provide support for both perspectives. The implications of the study’s findings are discussed