Local wave-number model for inhomogeneous two-fluid mixing

Abstract. Commonly, wave quantities are maintained in zonal mean averages. Hence, local wave phenomena remain unclear. Here, we introduce a diagnostic tool for studies of wave packets locally. The "Unified Wave Diagnosis" (UWaDi) uses the Hilbert Transform to obtain a complex signal from a real-valued function and estimates the amplitude and wave number locally. Operational data from the European Centre for Medium-Range Weather Forecasts is used to perform the analysis. Restrictions on gravity wave propagation due to model sponge layers are identified well above the 10 hPa altitude. From a minor stratospheric warming in January 2016 three cases for vertical gravity wave propagation in different background wind conditions are selected. It is shown that zonal mean wind quantities cannot reveal local "valves" allowing gravity waves to propagate into the mid-stratosphere. The unexpected finding of high gravity wave activity at the minor warming of 30 January 2016 is related to strong planetary wave activity and a strong local "pump". Accordingly, the advantages of a local wave packet analysis are demonstrated for profiles up to the model sponge layer.

Download Full-text

Two-fluid mixing in a microchannel

International Journal of Heat and Fluid Flow ◽

10.1016/j.ijheatfluidflow.2004.03.006 ◽

2004 ◽

Vol 25 (6) ◽

pp. 986-995 ◽

Cited By ~ 93

Author(s):

Ying Zheng Liu ◽

Byoung Jae Kim ◽

Hyung Jin Sung

Keyword(s):

Fluid Mixing ◽

Two Fluid

Download Full-text

A NEW LATTICE GAS MODEL FOR 1-D SOUND PROPAGATION

Journal of Computational Acoustics ◽

10.1142/s0218396x93000226 ◽

1993 ◽

Vol 01 (04) ◽

pp. 423-454 ◽

Cited By ~ 7

Author(s):

YASUSHI SUDO ◽

VICTOR W. SPARROW

Keyword(s):

Truncation Error ◽

Lattice Gas ◽

Sound Propagation ◽

Lattice Gas Model ◽

Wave Number ◽

General Boundary Condition ◽

Impedance Boundary ◽

Fluid Media ◽

Two Fluid ◽

The Continuum

A new lattice gas model for sound propagation in one space dimension is proposed. This model has zero truncation error, and the group velocity is independent of wave number as is required from the continuum limit. Conventional finite difference approaches do not have these properties in general. Boundary condition treatments, applicable to the lattice gas formulation, are also given. Both the boundary between two fluid media and an impedance boundary are considered.

Download Full-text

Modelling and numerical simulation of plasma flows with two-fluid mixing

European Journal of Mechanics - B/Fluids ◽

10.1016/j.euromechflu.2010.10.008 ◽

2011 ◽

Vol 30 (2) ◽

pp. 252-258 ◽

Cited By ~ 3

Author(s):

Rémi Sentis ◽

Didier Paillard ◽

Céline Baranger ◽

Patricia Seytor

Keyword(s):

Numerical Simulation ◽

Fluid Mixing ◽

Plasma Flows ◽

Two Fluid

Download Full-text

Proposed Use of the One-Dimensional Two-Fluid Model With Momentum Flux Parameters

10.1115/imece2000-2061 ◽

2000 ◽

Author(s):

Jin Ho Song ◽

H. D. Kim

Keyword(s):

Differential Equations ◽

Void Fraction ◽

Momentum Flux ◽

Fluid Model ◽

Sufficient Conditions ◽

Wave Number ◽

One Dimensional ◽

Two Fluid Model ◽

The One ◽

Two Fluid

Abstract The dynamic character of a system of the governing differential equations for the one-dimensional two-fluid model, where the appropriate momentum flux parameters are employed to consider the velocity and void fraction distribution in a flow channel, is analyzed. In response to a perturbation in the form of a traveling wave, a linear stability analysis is performed for the governing differential equations. The analytical expression for the growth factor as a function of wave number, void fraction, drag coefficient, and relative velocity is derived. It provides the necessary and sufficient conditions for the stability of the one-dimensional two-fluid model in terms of momentum flux parameters. It is analytically shown that the one-dimensional two-fluid model is mathematically well posed by use of appropriate momentum flux parameters, while the conventional two-fluid model makes the system unconditionally unstable. It is suggested that the velocity and void distributions should be properly accounted for in the one-dimensional two-fluid model by use of momentum flux parameters.

Download Full-text