Where does spatter collide?

In welding spatter is the scattering of molten metal droplets thrown out of the arc and weld pool that land and stick on the surrounding surface rather than joining the weld. It wastes filler, requires cleanup, and in excess signals poor parameter settings or a disturbed arc. Cary and Helzer's Modern Welding Technology covers the arc conditions, shielding, and current mode that raise or reduce it. The referent is ejected weld-metal droplets as a process loss, measured by the amount deposited around the weld, distinct from forensic bloodstains or the splash of an impacting drop.[1]

Unit

The quantity of ejected metal droplets deposited around the weld

Recovery means

Not applicable

Measured by

Assessed by deposited spatter mass or area and by cleanup required

In forensic science blood spatter, more properly bloodstain pattern analysis, reads the size, shape, and distribution of bloodstains at a scene to reconstruct how blood was shed, inferring the direction, force, and position of its source. The geometry of each stain and the overall pattern carry information about the events that produced them. James, Kish, and Sutton's Principles of Bloodstain Pattern Analysis sets out the theory and method. The referent is an evidentiary blood pattern interpreted to reconstruct an event, measured by stain dimensions and impact angle, unrelated to ejected weld metal or a laboratory drop splash.[2]

Unit

The dimensions, shape, and impact angle of bloodstains in a pattern

Recovery means

Not applicable

Measured by

Analysed by stain length-to-width ratio for impact angle and by directionality and distribution

In fluid dynamics spatter is the splashing of a liquid drop that strikes a surface hard enough to throw off a crown of smaller secondary droplets rather than simply spreading. Whether a drop spreads, recedes, bounces, or splatters is set by its speed, size, and surface tension, captured in dimensionless numbers such as the Weber and Reynolds numbers. Yarin's review Drop Impact Dynamics: Splashing, Spreading, Receding, Bouncing... surveys the mechanics and the splashing threshold. The referent is the secondary-droplet breakup of an impacting drop, measured by the splashing threshold and ejected-droplet statistics, distinct from weld spatter or forensic bloodstains.[3]

Unit

The splashing threshold and the size and number of secondary droplets ejected

Recovery means

Not applicable

Measured by

Characterised by Weber and Reynolds numbers at the splashing threshold and secondary-drop statistics