F. T. M. Nieuwstadt

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Transition to turbulence in pipe flow is one of the most fundamental and longest-standing problems in fluid dynamics. Stability theory suggests that the flow remains laminar for all flow rates, but in practice pipe flow becomes turbulent even at moderate speeds. This transition drastically affects the transport efficiency of mass, momentum, and heat. On the(More)
Results are presented from a large eddy simulation (LES) and wind tunnel study of the turbulence regime in a horizontally evolving sheared atmospheric convective boundary layer (CBL) capped by a temperature inversion. The wind tunnel part of the study has been conducted in the thermally stratified tunnel of the University of Karlsruhe. For the numerical(More)
We present in this paper high resolution, two-dimensional LDV measurements in a turbulent pipe flow of water over the Reynolds number range 5000–25000. Results for the turbulence statistics up to the fourth moment are presented, as well as power spectra in the near-wall region. These results clearly show that the turbulence statistics scaled on inner(More)
Modifications of turbulence regime in the sheared convective boundary layer (CBL) by a number of external nonbuoyant forcings are studied experimentally in a thermally stratified wind tunnel and numerically by means of large eddy simulation. This type of CBL is observed in the atmosphere when an originally neutral or stable air mass is advected over a(More)
An in vitro model using a parallel-plate fluid flow chamber is supposed to simulate in vivo fluid shear stresses on various cell types exposed to dynamic fluid flow in their physiological environment. The metabolic response of cells in vitro is associated with the wall shear stress. However, parallel-plate flow chambers have not been characterized for(More)
We present the results of an experimental investigation into the nature and structure of turbulent pipe flow at moderate Reynolds numbers. A turbulence regeneration mechanism is identified which sustains a symmetric traveling wave within the flow. The periodicity of the mechanism allows comparison to the wavelength of numerically observed exact traveling(More)
We show the use of a dimensionless parameter alpha h, in properly downscaling a parallel-plate flow chamber system for flow stimulation of bone cells under microgravity. The proper experimental regime for exposing cells to predictable levels of dynamic fluid shear stress requires: 1) alpha h < 2, based on the consequent quasi-parabolic form of the velocity(More)
BACKGROUND/AIMS Ligating the right lateral vitelline vein of chicken embryos (venous clip) results in cardiovascular malformations. These abnormalities are similar to malformations observed in knockout mice studies of components of the endothelin-1 (ET-1)/endothelin-converting enzyme-1/endothelin-A receptor pathway. In previous studies we demonstrated that(More)