Methods of determining the properties of a fluid body

Abstract

A method is disclosed of determining the properties of a fluid body in the form of a surface-attached droplet/bubble. A data set is stored describing a plurality of droplets/bubbles of different shapes, in which each shape is captured as a combination of two or more linear dimensional measurements. For each shape the data set includes one or more parameters describing the relationship between the physical properties of a pair of fluids capable of forming that shape as a surface-attached droplet/bubble disposed in a surrounding fluid medium. A fluid body is provided in the form of a surface-attached droplet/bubble and a plurality of linear dimensional measurements are taken and are provided as an input to a processing apparatus. The processing apparatus determines from the data set the one or more parameters associated with the shape described by said linear dimensional measurements. In particular the surface tension of a fluid can be found in this way based on simple dimensional measurements.

1 . A method of determining the properties of a fluid body in the form of a surface attached droplet/bubble, comprising the steps of:
 (a) storing, in a memory accessible by a processing apparatus, a set of data describing a plurality of droplets/bubbles of different shapes, wherein each shape is captured in said data set as a combination of two or more linear dimensional measurements, and wherein for each shape the data set includes one or more parameters describing the relationship between the physical properties of a pair of fluids capable of forming said shape when a first of said fluids is a surface-attached droplet/bubble disposed in a surrounding medium of the second of said fluids;   (b) providing a fluid body as a surface-attached droplet/bubble of a first fluid in a surrounding medium of a different second fluid;   (c) measuring a plurality of linear dimensional measurements of said fluid body;   (d) providing said measurements as an input to a processing apparatus; and   (e) said processing apparatus determining from said data set said one or more parameters associated with the shape described by said linear dimensional measurements.   
     
     
         2 . The method of  claim 1 , wherein one of the first and second fluids is known and the other is unknown, and wherein the properties of the known fluid permit the derivation from said one or more parameters of corresponding properties of the unknown fluid. 
     
     
         3 . The method of  claim 1 , wherein said one or more parameters comprise a parameter which is a function of an accelerating field, a surface tension of one fluid at the interface with the other fluid, and the respective fluid densities. 
     
     
         4 . The method of  claim 3  wherein the accelerating field is the local gravitational field as characterised by the acceleration due to gravity, g. 
     
     
         5 . The method of  claim 1 , wherein the two or more linear dimensional measurements are normalised measurements. 
     
     
         6 . The method of  claim 5 , wherein the two or more linear measurements are normalised against a further linear measurement of the bubble/drop. 
     
     
         7 . The method of  claim 6 , wherein the further linear measurement is a base diameter or base radius of the bubble drop at a surface to which it is attached. 
     
     
         8 . The method of  claim 1 , wherein the two or more linear dimensional measurements of the data set comprise any two of the following measurements normalised against the remaining measurement: height normal to attachment surface, maximum width parallel to attachment surface, and base diameter/radius at attachment surface. 
     
     
         9 . The method of  claim 1 , wherein the two or more linear dimensions of the data set are expressed as a combination of dimensions such as an area or a volume. 
     
     
         10 . The method of  claim 1 , wherein the data set is limited based on one or more of the following assumptions used to create the data set:
 (a) a value for one or more properties of the first fluid;   (b) a value for one or more properties of the second fluid;   (c) a value for one or more properties of the interface between first and second fluids   (d) a value for an acceleration such as gravitational acceleration, g.   
     
     
         11 . The method of  claim 1 , wherein said set of data comprises a plurality of parameter sets, each parameter set describing a unique solution to an equation modelling the shape of a droplet/bubble, and each parameter set including said combination of two or more linear dimensional measurements and said one or more parameters describing the relationship between the physical properties of a pair of fluids capable of providing said solution. 
     
     
         12 . A method of obtaining the interfacial surface tension between a liquid in a gas, comprising the steps of:
 performing the method of  claim 1  using a bubble of said gas in said liquid or a droplet of said liquid in said gas in step (b), wherein the resultant shape of the bubble/droplet is encompassed within the data set in step (a), wherein the one or more parameters describing the relationship between the physical properties of a pair of fluids include at least one parameter based on interfacial surface tension, said at least one parameter being determined in step (e).   
     
     
         13 . A computer program product comprising instructions encoded on a data carrier which, when executed in a computing system, are effective to:
 (a) receive as an input a plurality of linear dimensional measurements of a droplet/bubble;   (b) access a memory storing a set of data describing a plurality of droplets/bubbles of different shapes, wherein each shape is captured in said data set as a combination of two or more linear dimensional measurements, and wherein for each shape the data set includes one or more parameters describing the relationship between the physical properties of a pair of fluids capable of forming said shape when a first of said fluids is a surface-attached droplet/bubble disposed in a surrounding medium of the second of said fluids;   (c) determining from said data set said one or more parameters associated with the shape described by said linear dimensional measurements received as an input; and   (d) providing as an output said one or more parameters.   
     
     
         14 . An apparatus for determining the properties of a fluid body in the form of a surface-attached droplet/bubble, comprising:
 (a) a memory storing a set of data describing a plurality of droplets/bubbles of different shapes, wherein each shape is captured in said data set as a combination of two or more linear dimensional measurements, and wherein for each shape the data set includes one or more parameters describing the relationship between the physical properties of a pair of fluids capable of forming said shape when a first of said fluids is a surface-attached droplet/bubble disposed in a surrounding medium of the second of said fluids; (b) a processor programmed to receive as an input, a plurality of linear dimensional measurements of a a fluid body as a surface-attached droplet/bubble of a first fluid in a surrounding medium of a different second fluid providing said measurements as an input to a processing apparatus; and   (c) a program causing said processor to determine from said data set said one or more parameters associated with the shape described by said linear dimensional measurements.   
     
     
         15 . An apparatus as claimed in  claim 14 , further comprising a measurement system for making said plurality of linear dimensional measurements, and an output there from to said processor.