A Flat Plate Skin Friction Correlation Including Transition

Many existing boundary layer models treat transition as a rapid switch from laminar to turbulent flow, with correlations defining properties in each respective region. Natural transition, however, is not always a very spanwise uniform process, with the onset of transition varying somewhat between different streamwise paths of fluid flow. Thus, a spanwise average of natural transition can result in a more gradual, extended transition region than many existing models predict. Modern applications, such as aircraft wings and fuselages, are extremely streamlined and smooth, allowing for natural transition to occur rather than flow tripping to turbulent near the leading edge. Under these conditions, a skin friction model that takes this extended transition region into account provides a more accurate model compared to those which incorporate a rapid transition from laminar to turbulent flow. Lienhard’s recent publication 1 presents a new rationale for modeling the extent of the transition region on a smooth flat plate developed from re-analysis of existing heat transfer data. This correlation accounts for the extended natural transition region corresponding to a spanwise average of values. The primary objective of this thesis was to reinterpret Lienhard’s heat transfer correlation to solve for skin friction coefficient, then compare this correlation to available experimental data and higher order boundary layer models. After reinterpreting Lienhard’s correlation using the Reynolds analogy, it produced a gradual, extended transition region for skin friction coefficient. The reinterpreted correlation had excellent agreement with experimental data corresponding to a spanwise average of flow with natural transition. Tripped transitional values and data taken along a streamwise path of fluid resulted in a more rapid transition from laminar to turbulent flow. Both an integral boundary layer model and a Reynolds-averaged Navier-Stokes boundary layer model were used to validate the reinterpreted Lienhard correlation. Both of these models produced transition curves steeper than the reinterpreted Lienhard curve. These existing boundary layer models do not take into account the gradual transition region that natural transition may produce when looking at a spanwise average of values. With a focus on spanwise averaged values, such as overall drag over a streamlined surface, existing sophisticated boundary layer models may not accurately predict the behavior produced. The reinterpreted Lienhard correlation provides a new representation of skin friction coefficient throughout the boundary layer that takes into account the extended transition region that may occur when it is desired to model a spanwise average of fluid flow. 1Lienhard, J. Heat transfer in flat-plate boundary layers: A correlation for laminar, transitional, and turbulent flow. ASME Journal of Heat Transfer, 142, 2020

Basel III B: Basel III Overview

In the wake of the financial crisis of 2007-09, the Basel Committee on Banking Supervision (BCBS) faced the critical task of diagnosing what went wrong and then updating regulatory standards aimed at preventing it from occurring again. In seeking to strengthen the microprudential regulation associated with the earlier Basel Accords while also adding a macroprudential overlay, Basel III consists of proposals in three main areas intended to address 1) capital reform, 2) liquidity standards, and 3) systemic risk and interconnectedness. This case considers the causes of the 2007-09 financial crisis and what they suggest about weaknesses in the Basel regime as it then existed. It then summarizes the provisions of Basel III to allow for an evaluation of whether it was an effective response to the causes of the financial crisis

Patterns of item nonresponse behaviour to survey questionnaires are systematic and associated with genetic loci

Peer reviewe

Large-scale GWAS reveals insights into the genetic architecture of same-sex sexual behavior.

Twin and family studies have shown that same-sex sexual behavior is partly genetically influenced, but previous searches for specific genes involved have been underpowered. We performed a genome-wide association study (GWAS) on 477,522 individuals, revealing five loci significantly associated with same-sex sexual behavior. In aggregate, all tested genetic variants accounted for 8 to 25% of variation in same-sex sexual behavior, only partially overlapped between males and females, and do not allow meaningful prediction of an individual's sexual behavior. Comparing these GWAS results with those for the proportion of same-sex to total number of sexual partners among nonheterosexuals suggests that there is no single continuum from opposite-sex to same-sex sexual behavior. Overall, our findings provide insights into the genetics underlying same-sex sexual behavior and underscore the complexity of sexuality