91,497 research outputs found
Data from DNS of Fourier-Filtered Rough Surfaces
No full textData created and presented by F. Alves Portela, A. Busse N. D. Sandham, "Numerical Study of Fourier-Filtered Rough Surfaces". Physical Review Fluids. 2021 (doi: 10.1103/PhysRevFluids.6.084606) as well as height maps of the five surfaces considered.</span
Inertial convection in rotating fluid spheres
Get PDFThe onset of convection in the form of inertial waves in a rotating fluid sphere is studied through a perturbation analysis in an extension of earlier work by Zhang (1994). Explicit expressions for the dependence of the Rayleigh number on the azimuthal wavenumber are derived and new results for the case of a nearly thermally insulating boundary are obtained
The Karlsruhe two-scale dynamo experiment
No full textThis article outlines the experimental realization of the Roberts-Busse kinematic dynamo model at the Forschungszentrum Karlsruhe. Essential observations of the spatial and temporal structures of the self-induced magnetic field and features of its saturation mechanism are presented and the experimental findings are compared with predictions from model calculations
Rechtsgeschäftliches Handeln autonomer, intelligenter Systeme
No full textBusse F. Rechtsgeschäftliches Handeln autonomer, intelligenter Systeme. Studien zur Rechtswissenschaft. Vol 465. Hamburg: Verlag Dr. Kovac; 2022
L. Busse: Leib und Seele. Zeitschr. f. Philos. u. philos. Krit. 114 (1), 1-26. 1899 / F. Paulsen: Noch ein Wort zur Theorie des Parallelismus. Ebenda 115 (1), 1-9. 1899
No full textL. BUSSE: LEIB UND SEELE. ZEITSCHR. F. PHILOS. U. PHILOS. KRIT. 114 (1), 1-26. 1899 / F. PAULSEN: NOCH EIN WORT ZUR THEORIE DES PARALLELISMUS. EBENDA 115 (1), 1-9. 1899
Zeitschrift für Psychologie und Physiologie der Sinnesorgane (-)
Zeitschrift für Psychologie und Physiologie der Sinnesorgane (22) (a0006)
L. Busse: Leib und Seele. Zeitschr. f. Philos. u. philos. Krit. 114 (1), 1-26. 1899 / F. Paulsen: Noch ein Wort zur Theorie des Parallelismus. Ebenda 115 (1), 1-9. 1899 (22) (p0220
M. Schmaus, J. R. Geiselmann, H. Rahner. Handbuch der Dogmengeschichte, B. IV, F. 3 : Busse und Letzte Oelung
No full textNautin Pierre. M. Schmaus, J. R. Geiselmann, H. Rahner. Handbuch der Dogmengeschichte, B. IV, F. 3 : Busse und Letzte Oelung. In: Revue de l'histoire des religions, tome 146, n°1, 1954. pp. 122-123
Parametric forcing approach to rough-wall turbulent channel flow
Get PDFThe effects of rough surfaces on turbulent channel flow are modelled by an extra force term in the Navier–Stokes equations. This force term contains two parameters, related to the density and the height of the roughness elements, and a shape function, which regulates the influence of the force term with respect to the distance from the channel wall. This permits a more flexible specification of a rough surface than a single parameter such as the equivalent sand grain roughness. The effects of the roughness force term on turbulent channel flow have been investigated for a large number of parameter combinations and several shape functions by direct numerical simulations. It is possible to cover the full spectrum of rough flows ranging from hydraulically smooth through transitionally rough to fully rough cases. By using different parameter combinations and shape functions, it is possible to match the effects of different types of rough surfaces. Mean flow and standard turbulence statistics have been used to compare the results to recent experimental and numerical studies and a good qualitative agreement has been found. Outer scaling is preserved for the streamwise velocity for both the mean profile as well as its mean square fluctuations in all but extremely rough cases. The structure of the turbulent flow shows a trend towards more isotropic turbulent states within the roughness layer. In extremely rough cases, spanwise structures emerge near the wall and the turbulent state resembles a mixing layer. A direct comparison with the study of Ashrafian, Andersson & Manhart (Intl J. Heat Fluid Flow, vol. 25, 2004, pp. 373–383) shows a good quantitative agreement of the mean flow and Reynolds stresses everywhere except in the immediate vicinity of the rough wall. The proposed roughness force term may be of benefit as a wall model for direct and large-eddy numerical simulations in cases where the exact details of the flow over a rough wall can be neglecte
Numerical simulations of rotating axisymmetric sunspots
No full textA numerical model of axisymmetric convection in the presence of a vertical magnetic flux bundle and rotation about the axis is presented. The model contains a compressible plasma described by the non-linear MHD equations, with density and temperature gradients simulating the upper layer of the Sun's convection zone. The solutions exhibit a central magnetic flux tube in a cylindrical numerical domain, with convection cells forming collar flows around the tube. When the numerical domain is rotated with a constant angular velocity, the plasma forms a Rankine vortex, with the plasma rotating as a rigid body where the magnetic field is strong, as in the flux tube, while experiencing sheared azimuthal flow in the surrounding convection cells, forming a free vortex. As a result, the azimuthal velocity component has its maximum value close to the outer edge of the flux tube. The azimuthal flow inside the magnetic flux tube and the vortex flow is prograde relative to the rotating cylindrical reference frame. A retrograde flow appears at the outer wall. The most significant convection cell outside the flux tube is the location for the maximum value of the azimuthal magnetic field component. The azimuthal flow and magnetic structure are not generated spontaneously, but decay exponentially in the absence of any imposed rotation of the cylindrical domain
Forced phase diffusion in a convection experiment
No full textIn a thermal-convection box the boundaries parallel to the convection rolls are replaced by ramps, i.e., smooth variations in the Rayleigh number from supercritical to subcritical values. Such a geometry selects a small wavelength band. The wavelength selected by the left and right ramps are not necessarily the same�resulting in a wavelength gradient. This gradient leads to forced phase diffusion: The convection pattern drifts from the short-wavelength end to the ramp selecting the longer wavelength. An experimental observation of this phenomenon is presented
Change in drag, apparent slip and optimum air layer thickness for laminar flow over an idealised superhydrophobic surface
Get PDFAnalytic results are derived for the apparent slip length, the change in drag and the optimum air layer thickness of laminar channel and pipe flow over an idealised superhydrophobic surface, i.e. a gas layer of constant thickness retained on a wall. For a simple Couette flow the gas layer always has a drag reducing effect, and the apparent slip length is positive, assuming that there is a favourable viscosity contrast between liquid and gas. In pressure-driven pipe and channel flow blockage limits the drag reduction caused by the lubricating effects of the gas layer; thus an optimum gas layer thickness can be derived. The values for the change in drag and the apparent slip length are strongly affected by the assumptions made for the flow in the gas phase. The standard assumptions of a constant shear rate in the gas layer or an equal pressure gradient in the gas layer and liquid layer give considerably higher values for the drag reduction and the apparent slip length than an alternative assumption of a vanishing mass flow rate in the gas layer. Similarly, a minimum viscosity contrast of four must be exceeded to achieve drag reduction under the zero mass flow rate assumption whereas the drag can be reduced for a viscosity contrast greater than unity under the conventional assumptions. Thus, traditional formulae from lubrication theory lead to an overestimation of the optimum slip length and drag reduction when applied to superhydrophobic surfaces, where the gas is trapped
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