Direct numerical simulations of instability and boundary layer turbulence under a solitary wave

Author Posting. © Cambridge University Press, 2013. This article is posted here by permission of Cambridge University Press for personal use, not for redistribution. The definitive version was published in Journal of Fluid Mechanics 731 (2013): 545-578, doi:10.1017/jfm.2013.361 .A significant amount of research effort has been made to understand the boundary layer instability and the generation and evolution of turbulence subject to periodic/oscillatory flows. However, little is known about bottom boundary layers driven by highly transient and intermittent free-stream flow forcing, such as solitary wave motion. To better understand the nature of the instability mechanisms and turbulent flow characteristics subject to solitary wave motion, a large number of direct numerical simulations are conducted. Different amplitudes of random initial fluctuating velocity field are imposed. Two different instability mechanisms are observed within the range of Reynolds number studied. The first is a short-lived, nonlinear, long-wave instability which is observed during the acceleration phase, and the second is a broadband instability that occurs during the deceleration phase. Transition from a laminar to turbulent state is observed to follow two different breakdown pathways: the first follows the sequence of $K$-type secondary instability of a near-wall boundary layer at comparatively lower Reynolds number and the second one follows a breakdown path similar to that of free shear layers. Overall characteristics of the flow are categorized into four regimes as: (i) laminar; (ii) disturbed laminar; (iii) transitional; and (iv) turbulent. Our categorization into four regimes is consistent with earlier works. However, this study is able to provide more specific definitions through the instability characteristics and the turbulence breakdown process.This study is supported by National Science Foundation (CMMI-1135026; OCE- 1130217; OCE-1131016).2014-08-2

The left sternalis muscle variation detected during mastectomy

The sternalis muscle variation is a well-known anatomical situation. It is present in 8.7% of women and 6.4% of men, although the incidence varies according to sex, race and ethnicity. During a left modified radical mastectomy operation on a 46-year-old female patient a sternalis muscle was detected on the pectoralis major muscle in the superficial fascia. It was in craniocaudal position and was parallel to the body of the sternum. The cylindrical muscle was approximately 8 cm in length and 2 cm in diameter. Such variations are considered to have their origin in embryological development. Awareness of muscular variations and their identification is important both for procedure through the proper dissection planes during breast surgery and in radiological examination and follow-up