Yaa Application Of Ultrasound Inward The Grooming Of Cotton Fiber Too Silk Stuff (Part-1)

Application of Ultrasound inwards the Preparation of Cotton as well as Silk Fabric (Part-1)

Utpal Mondal

Govt. College of Engineering as well as Textile Technology
Berhampore, Murshidabad, India
Email: utpal.khs.gcettb07@gmail.com

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1. INTRODUCTION
1.1 Sound:
Sound is a shape of energy, only similar electricity as well as light. Sound is made when air molecules vibrate as well as displace inwards a designing called waves, or audio waves [1].

1.2 Ultrasound:
Sound generated inwards a higher house the human hearing make (20 Hz to xx kHz) is called ultrasound. Ultrasonic vibrations go inwards the shape of a wave, similar to light. However, dissimilar low-cal waves, which tin go inwards a vacuum (empty space); ultrasound requires an elastic medium such every bit a gas, liquid or solid. However, the frequency make commonly employed inwards ultrasonic non-destructive testing as well as thickness make is 100 kHz to fifty MHz. Although ultrasound behaves inwards a similar trend to audible sound, it has a much shorter wavelength [2].

1.3 History:
The earliest shape of an ultrasonic transducer was a whistle developed past times Sir Francis Galton (1822-1911) inwards 1883 to investigate threshold frequency of human hearing.

The commencement commercial application of ultrasonic appeared about 1917 as well as was the commencement “eco-sounder” invented as well as developed past times Paul Langévin (1872-1946). The master copy “echo-sounder” eventually became underwater audio navigation as well as ranging for submarine detection during World War 2 [3].

2. GENERAL PRINCIPLE
2.1 Introduction:
Being a audio wave, ultrasound is transmitted through whatever substance, solid, liquid or gas which possess elastic properties. The motion of the vibrating trunk is communicated to the molecules of the medium, each of which transmits the displace to an adjoining molecule earlier returning to unopen to its master copy position. For liquids as well as gases, particle oscillation takes house inwards the direction of the moving ridge as well as produces longitudinal waves (In a longitudinal moving ridge the particle displacement is parallel to the direction of moving ridge propagation) (fig.1a). Solids, however, they every bit good possess shear elasticity, tin every bit good back upwardly tangential stresses giving ascent to transverse waves (In a transverse moving ridge the particle displacement is perpendicular to the direction of moving ridge propagation), inwards which particle motion takes house perpendicular to the direction of the moving ridge (fig. 1b) [3].

Figure. 1: Wave particle movement; (a) longitudinal waves; (b) transverse waves.

2.2 Bubble formation as well as the factors affecting cavitation threshold:

A bubble is a globule (small circular particles) of i meat inwards another, usually gas inwards a liquid. Due to the marangoni number (the volume transfer along an interface betwixt 2 fluids due to surface tension gradient), bubbles may stay intact when they plough over the surface of the immersive meat [].

Cavitation is the formation of vapour cavities inwards liquid i.e. modest liquid-cavitation-free zones (“bubbles” or “void”)-that are the consequencies of cavitational forces acting upon the cavitational liquid. It usually occurs when a liquid is subjected to rapid changes of pull per unit of measurement area that crusade the formation of cavities where the pull per unit of measurement area is relatively depression [4].

The effects are every bit follows:
2.2.1 Effect of gas as well as particulate matter:
The progression of a audio moving ridge through a liquid medium caused the molecules to oscillate nearly their hateful position. During the compression cycle, the average distance betwixt the molecules decreased, whilst during rarefaction the distances increased. If a sufficiently large negative pull per unit of measurement area is applied to the liquid, such that the average distance betwixt the molecules exceeds the critical molecular distance necessary to concur the liquid intact, the liquid volition interruption downwardly as well as voids or cavities volition live created i.e. cavitation bubbles volition live formed (cavitation is the formation of gas bubbles of a flowing liquid inwards a portion where the pull per unit of measurement area of the liquid falls below its vapour pressure. Cavitation is usually divided into 2 classes of behaviour: inertial cavitation, as well as non-inertial cavitation). Once produced these cavities, voids or bubbles, may grow inwards size until the maximum of the negative pull per unit of measurement area has been reached.

Figure. 2: Erosion of (a) initial surface; (b) eroded surface

Estimates of the acoustic pull per unit of measurement area necessary to crusade cavitation inwards H2O has led to a value of unopen to 1500 atm. In practise cavitation occurs at considerably lower values as well as this is undoubtedly due to the presence of weak-spots inwards the liquid which lower the liquid’s tensile strength. There is straight off sufficient experimental prove to propose that i crusade of weak-spots is the presence of gas molecules inwards liquid. For instance it has been observed that the degassing of liquids has led to increment inwards the cavitation threshold i.e. to increment inwards the values of the applied acoustic pull per unit of measurement area necessary earlier cavitation bubbles were observed. Further, the application of external pull per unit of measurement area which would crusade whatever suspended gas molecules to dissolve, thereby effectively removing the gas nuclei, has every bit good been constitute to Pb to increases inwards the cavitation threshold.

To do bubble inwards water, render the maximum rarefaction. Thus in that location volition likely live several different types of cavity inwards the liquid:

• The empty cavity (true cavitation),
• The vapour filled cavity,
• The gas filled cavity, unless the liquid is totally degassed, as well as
• A combination of vapour as well as gas filled cavities [3].

2.2.2 Effects of viscosity:
Since it is necessary for the negative pull per unit of measurement area inwards the rarefaction wheel to overcome the natural cohesive forces acting inwards the liquid, whatever increment inwards these forces volition increment the threshold of cavitation. One method of increasing these forces is to increment the viscosity of the liquid.

The effect, though non insignificant, is hardly dramatic. Taking corn as well as castor oils every bit examples, a ten-fold increment inwards viscosity has exclusively led to a 30% increment inwards the acoustic pull per unit of measurement area needed convey nearly cavitation [3].

2.2.3 Effects of applied frequency:
To completely rupture a liquid as well as so render a void, which may later piece of job filled alongside gas or vapour, requires a finite time. For audio waves alongside high frequencies, the fourth dimension required to do the bubble may live longer than available during the rarefaction cycle. Thus it mightiness anticipated that every bit the frequency increases the production of cavitation bubbles piece of job to a greater extent than hard to attain inwards the available fourth dimension as well as the greater audio intensities volition require to live employed, over these shorter periods, to ensure that the cohesive forces of the liquid are overcome.

Figure. 3: Variation inwards threshold intensity alongside frequency; (a) aerated water; (b) air gratis H2O [3]

2.2.4 Effect of temperature:
The concluding constituent to live considered here, as well as known to touching the cavitation threshold, is the temperature. In full general the threshold boundary has been constitute to increment alongside decrease inwards temperature. This may inwards business office live due to increases inwards either the surface tension or viscosity of the liquid every bit the temperature decreases, or it may live due to the decreases inwards liquid vapour pull per unit of measurement area [3].

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