Skimming impact of a thin heavy body on a shallow liquid layer

This study addresses the question of whether a thin, relatively heavy solid body with a smooth under-surface can skim on a shallow layer of liquid (for example water), i.e. impact on the layer and rebound from it. The body impacts obliquely onto the liquid layer with the trailing edge of the underbody making the initial contact. The wetted region then spreads along the underbody and eventually either retracts, generating a rebound, or continues to the leading edge of the body and possibly leads to the body sinking. The present inviscid study involves numerical investigations for increased mass ( M , in scaled terms) and moment of inertia ( I , proportional to the mass) together with an asymptotic analysis of the influential parameters and dynamics at different stages of the skimming motion. Comparisons between the asymptotic analysis and numerical results show close agreement as the body mass becomes large. A major finding is that, for a given impact angle of the underbody relative to the liquid surface, only a narrow band of initial conditions is found to allow the heavy-body skim to take place. This band includes reduced impact velocities of the body vertically and rotationally, both decreasing like M−2/3 , while the associated total time of the skim from entry to exit is found to increase like M1/3 typically. Increased mass thereby enhances the super-elastic behaviour of the skim

The role of body shape and mass in skimming on water

Over many years, there has been great practical interest in how solid bodies interact with and skim on liquid layers. In the present investigation, the focus is on the important role of body mass and shape in such skimming motions. Considering a thin two-dimensional solid body that impacts obliquely and then rebounds on a shallow inviscid water layer, we develop a mathematical model to predict quantitatively the duration and evolution of the body and fluid motions and indeed the success or failure of the whole skim. In the current setting, the shallow water layer thickness is small relative to the representative body length. The combined roles of increased mass and shape are found to be crucial, governed by a similarity solution. The relationship C ∼ M2/3 between scaled body curvature and mass is identified and highlighted. In particular, increased convex curvature of the underbody is found to alter the interactive pressure in such a way that it inhibits the occurrence of a super-elastic response in the exit vertical velocity and height of the body, and in effect enables a much heavier body to skim successfully provided the above relationship is maintained

A body in nonlinear near-wall shear flow:impacts, analysis and comparisons

Interaction between body motion and fluid motion is considered inside a nonlinear viscous wall layer, with this unsteady two-way coupling leading to impact of the body on the wall. The present paper involves a reduced system analysis which is shown to be consistent with computational solutions from direct numerical simulations for a basic flat-plate shape presented in an allied paper (Palmer & Smith, J. Fluid Mech., 2020). The occurrence of impact depends mainly on fluid parameters and initial conditions. The body considered is translating upstream or downstream relative to the wall. Subsequent analysis focusses on the unusual nature of the impact at the leading edge. The impacting flow structure is found to have two nonlinear viscous–inviscid regions lying on either side of a small viscous region. The flow properties in the regions dictate the lift and torque which drive the body towards the wall. Pronounced flow separations are common as the impact then cuts off the mass flux in the gap between the body and the wall; here, a nonlinear similarity solution sheds extra light on the separations. Comparisons are made between results from direct simulations and asymptotics at increased flow rate

The development of a measure of social care outcome for older people. Funded/commissioned by: Department of Health

An essential element of identifying Best Value and monitoring cost-effective care is to be able to identify the outcomes of care. In the field of health services, use of utility-based health related quality of life measures has become widespread, indeed even required. If, in the new era of partnerships, social care outcomes are to be valued and included we need to develop measures that reflect utility or welfare gain from social care interventions. This paper reports on a study, commissioned as part of the Department of Health’s Outcomes of Social Care for Adults Initiative, that developed an instrument and associated utility indexes that provide a tool for evaluating social care interventions in both a research and service setting. Discrete choice conjoint analysis used to derive utility weights provided us with new insights into the relative importance of the core domains of social care to older people. Whilst discrete choice conjoint analysis is being increasingly used in health economics, this is the first study that has attempted to use it to derive a measure of outcome

Exploring the Policy Implications of the Surface Mining Control and Reclamation Act

This paper explores how policy structure, institutions, and political climate impact the ability of the Surface Mining Control and Reclamation Act (SMCRA) to ensure the reclamation of surface coal mines. We conduct a policy review that traces the impacts of the three parts of SMCRA; Reclamation Standards, Reclamation Bonding Requirements, and the Abandoned Mine Land fund. We examine the implications the act and its approach have for the mining industry and their ability to reclaim mining areas. We find that each of the three parts of SMCRA’s approach face substantial problems in their implementation. Though largely a positive force for internalizing the environmental costs of surface mining, those issues commonly elucidated in the public choice literature reduce the efficacy of the policy approach and call into question the act’s ability to ensure reclamation occurs. Both in the structure of the bonding requirements and in the regulatory structure created by the act, misaligned incentives sometimes hamper effective reclamation. Further, the funds created under SMCRA to reclaim and restore mined lands have often been directed towards projects that are politically expedient for politicians instead of those that would best serve the fund’s original reclamation purpose. After revealing these problems and putting them in the context of the public choice literature, we suggest updates to the current policy that would align reclamation incentives and better ensure that the reclamation of surface mines occurs. We emphasize the cooperative elements of SMCRA and suggest how other countries, especially those without major existing frameworks for handling reclamation, can emulate the successes of SMCRA while avoiding its implementations snags

Building a Quality of Life Index

This chapter outlines how an index measuring quality of life should be developed and then applies that work at the county level in the United States. The index we create is a unique and data‐driven approach to calculating quality of life. In the chapter, we explain the process that leads us to selecting our five indicators: public safety, health, economic development, infrastructure, and education. Each indicator breaks apart into subindicators. This chapter theoretically and statistically verifies our chosen indicators. First, we develop theoretical arguments explaining the connections between quality of life and our indicators. Then, we perform confirmatory factor analyses on our index to empirically verify our theoretical arguments for why each component should be included in the index. Further, we finally verify our theory and index using survey results. We use only publicly available data to facilitate replication by others. The results of our confirmatory factor analysis provide statistical evidence for our choice of indicators in measuring quality of life. Our findings indicate that those measuring quality of life must account for the roles of: public safety, health, economic development, infrastructure, and education. Most importantly, our results indicate that our index is a valid measure of quality of life

A case study of youth participatory evaluation in co-curricular service learning

Abstract: This paper examines the practice of participatory evaluation through an exploratory single case study of the Evaluation Team of Books & Beyond, a cocurricular service-learning program of the Global Village Living-Learning Center at Indiana University. The paper, which is authored by three undergraduate members of the evaluation team and their faculty advisor, juxtaposes the process of conducting the evaluation and reporting the results with reflections from the Evaluation Team participants on conducting youth participatory action research, which offers a means of improving youth-serving programs and developing a greater understanding of why youth choose to participate in these programs. In their review of the implementation of their evaluation project, the team noted that the difficulties of getting past lessons learned to methodological rigor in service-learning evaluation are compounded by the realities of engaging in a student-faculty partnership in a co-curricular service-learning context