1980
DOI: 10.1029/gl007i002p00121
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Threshold windspeeds for sand on Mars: Wind tunnel simulations

Abstract: Wind friction threshold speeds (u*t) for particle movement (saltation) were determined in a wind tunnel operating at martian surface pressure with a 95 percent CO2 and 5 percent air atmosphere. The relationship between friction speed (u*) and free‐stream velocity (u∞) is extended to the critical case for Mars of momentum thickness Reynolds numbers (Reθ) between 425 and 2000. It is determined that the dynamic pressure required to initiate saltation is nearly constant for pressures between 1 bar (Earth) and 4 mb… Show more

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Cited by 226 publications
(223 citation statements)
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“…Figure 4 shows suspension and saltation thresholds as a function of particle diameter. Saltation threshold curves for larger sized particles were generated in the MARSWIT from previous experiments [Greeley et al, 1994]. All results presented in Figure 4 apply for equivalent Martian conditions in MARSWIT for the aerodynamically smooth-flow case.…”
Section: Discussion Of Smooth-surface Experimentsmentioning
confidence: 99%
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“…Figure 4 shows suspension and saltation thresholds as a function of particle diameter. Saltation threshold curves for larger sized particles were generated in the MARSWIT from previous experiments [Greeley et al, 1994]. All results presented in Figure 4 apply for equivalent Martian conditions in MARSWIT for the aerodynamically smooth-flow case.…”
Section: Discussion Of Smooth-surface Experimentsmentioning
confidence: 99%
“…Information about the MARSWIT facility has been documented [Greeley et al, , 1980[Greeley et al, , 1981. Particle suspension was detected using two methods.…”
Section: Experimental Facility and Measuring Systemsmentioning
confidence: 99%
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“…However, the physics of this lifting is still not fully understood. Wind tunnel experiments [Greeley et al, 1980[Greeley et al, , 1981 indicate that sand-sized particles of 100 mm in diameter are most easily moved via shear stress from horizontal winds. Smaller particles resist movement either because they are aerodynamically smooth [Bagnold, 1941] and/or because they develop inter-particle forces (possibly electrical in nature) [Iversen, 1976].…”
Section: Martian Atmospheric Dustmentioning
confidence: 99%
“…1). However, two mechanisms compete for making saltation on Mars very different from what it is on Earth: (i) Martian conditions require 10 times higher wind velocities than Terrestrial ones (13,14), being seen only a few times a decade during gusts of extreme aeolian activity (2,3,5,(15)(16)(17)(18)(19); and (ii) the lower gravity and stronger winds of Mars allow particles, once in the air, to fly higher and to remain longer in the atmosphere, being accelerated by the wind more than they are on Earth (8,20). From wind tunnel experiments under low-pressure conditions that reproduce the density of the Martian air, we could already gain some flavor of the efficiency of such high-speed saltating particles in dislodging sand grains or raising dust when colliding onto Martian soils (4).…”
mentioning
confidence: 99%