# Spanwise homogeneous buoyancy-drag model for Rayleigh-Taylor mixing and experimental evaluation

## Abstract

A buoyancy-drag model for Rayleigh-Taylor (RT) mixing is developed on the premise that the bubble and spike regions behave as distinct and spanwise homogeneous fluids. Then, mass conservation is applied accross the mixing zone to obtain their average mixture densities dynamically. These are used to explicitly calculate the inertia and buoyancy terms in the evolutionary equation. The only unknown parameter in the model is the Newtonian drag constant C{approx}2.5{+-}0.6, which is determined from turbulent RT experiments over various Atwood numbers A and acceleration histories g(t). The bubble (i=2) and spike (i=1) amplitudes are found to obey the familiar h{sub i}={alpha}{sub i}Agt{sup 2} for a constant g and h{sub i}{approx}t{sup {theta}{sub i}} for an impulsive g. For bubbles, both {alpha}{sub 2} and {theta}{sub 2} are insensitive to A. For the spikes, both {alpha}{sub 1} and {theta}{sub 1} increase as a power law with the density ratio. However, {theta}{sub 1} is not universal because it depends on the initial value of h{sub 1}/h{sub 2}. (c) 2000 American Institute of Physics.

- Authors:

- Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

- Publication Date:

- OSTI Identifier:
- 20216534

- Resource Type:
- Journal Article

- Journal Name:
- Physics of Plasmas

- Additional Journal Information:
- Journal Volume: 7; Journal Issue: 6; Other Information: PBD: Jun 2000; Journal ID: ISSN 1070-664X

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; RAYLEIGH-TAYLOR INSTABILITY; MIXING; DRAG; PLASMA FLUID EQUATIONS; BUBBLES; TURBULENCE; PLASMA INSTABILITY; EXPERIMENTAL DATA; THEORETICAL DATA

### Citation Formats

```
Dimonte, Guy.
```*Spanwise homogeneous buoyancy-drag model for Rayleigh-Taylor mixing and experimental evaluation*. United States: N. p., 2000.
Web. doi:10.1063/1.874060.

```
Dimonte, Guy.
```*Spanwise homogeneous buoyancy-drag model for Rayleigh-Taylor mixing and experimental evaluation*. United States. doi:10.1063/1.874060.

```
Dimonte, Guy. Thu .
"Spanwise homogeneous buoyancy-drag model for Rayleigh-Taylor mixing and experimental evaluation". United States. doi:10.1063/1.874060.
```

```
@article{osti_20216534,
```

title = {Spanwise homogeneous buoyancy-drag model for Rayleigh-Taylor mixing and experimental evaluation},

author = {Dimonte, Guy},

abstractNote = {A buoyancy-drag model for Rayleigh-Taylor (RT) mixing is developed on the premise that the bubble and spike regions behave as distinct and spanwise homogeneous fluids. Then, mass conservation is applied accross the mixing zone to obtain their average mixture densities dynamically. These are used to explicitly calculate the inertia and buoyancy terms in the evolutionary equation. The only unknown parameter in the model is the Newtonian drag constant C{approx}2.5{+-}0.6, which is determined from turbulent RT experiments over various Atwood numbers A and acceleration histories g(t). The bubble (i=2) and spike (i=1) amplitudes are found to obey the familiar h{sub i}={alpha}{sub i}Agt{sup 2} for a constant g and h{sub i}{approx}t{sup {theta}{sub i}} for an impulsive g. For bubbles, both {alpha}{sub 2} and {theta}{sub 2} are insensitive to A. For the spikes, both {alpha}{sub 1} and {theta}{sub 1} increase as a power law with the density ratio. However, {theta}{sub 1} is not universal because it depends on the initial value of h{sub 1}/h{sub 2}. (c) 2000 American Institute of Physics.},

doi = {10.1063/1.874060},

journal = {Physics of Plasmas},

issn = {1070-664X},

number = 6,

volume = 7,

place = {United States},

year = {2000},

month = {6}

}