The friction or the deformation drag f d of the sphere moving at a constant velocity v through a fluid of infinite extend is given by stokes law with the following assumptions. Mar 07, 2014 falling sphere viscometer a viscometer is an instrument used to measure the viscosity of a fluid. In the honour of hagenpoiseuille the unit of viscosity is called the poise p. Thus the viscosity of the liquid can be calculated by determin ing the falling time of the sphere at a known density of the liq uid. Extrapolation procedures for zero shear viscosity with a. This device is widely used to see the quality of fuel in the engines. Dynamic viscosity, the coefficient of proportionality between velocity gradient and sheer stress in a liquid, characterises how difficult it is for an object to flow.
A lower fluid viscosity results in less resistance to flow, which corresponds to a faster velocity of the moving object. A falling ball viscometer has a sphere ball that falls down along a tube containing the sample liquid to be measured, and this tube is surrounded concentrically by a tubular jacket for thermal control. The camera magnification is predetermined by photographing a scale immersed in the fall space. Pdf data acquisition system for a fallingsphere viscometer. Pdf measurement of viscosity in a vertical falling ball viscometer. The falling ball viscometer is based on stokes law. The previous theory used newtons law of motion for describing the falling ball reaching a terminal velocity. The ball is placed in the fluid and the time that it takes to fall the length of the cylinder is recorded. Measurement of terminal velocity of a ball falling in a viscous fluid enclosed in a narrow tube provides a method for determination of the coefficient of viscosity. Insert the viscometer into a holder and place in constant temperature bath.
This method applies the newtons law of motion with the acceleration term and corrected stokeslaw to derive the solution in terms of the viscosity and the falling time. Falling sphere viscometer this viscometer is covered in bs188 and is based on measuring the time for a small sphere to fall in a viscous fluid from one level to another. When utilizing stokes law, it is appropriate to verify the application of this law is appropriate. Viscometer rheosense high shear viscometer rheosense. Other simple designs include falling sphere, falling piston, rolling ball, and oscillating piston viscometers. Viscometers visual encyclopedia of chemical engineering. As the name implies, these viscometers use a falling sphere to measure viscosity. Pdf a commonly used apparatus in undergraduate physics laboratory environment is the falling sphere viscometer or stokes viscometer. The calculated value for the viscosity of water is r l % p r l0. Absolute falling ball viscometer, adapted to the low viscosities of. The method applies newtons law of motion under force balance on a falling sphere ball when it reaches a terminal velocity. Pdf design of a high precision fallingball viscometer.
Falling sphere viscometer constant temperature bcth 25t0 005 c j lloyd sutterbyt process fundamentals research laboratory, the dow chemical company, midland, michigan 48640, usa receiaed 6 nogember 1972, in fiiial form 24 may 1973 abstract a wide range, precision falling sphere viscometer is described. The basic concept is to measure the elapsed time required for the ball to fall under gravity through a samplefilled tube inclined at an angle. Stokes law can be used to calculate the viscosity of the fluid. This type of viscometer consists of a circular cylinder filled by the liquid under investigation. Vibrational viscometer helps to measure an oscillating electromechanical resonator that is immersed in a particular fluid. Turn the viscometer to normal position and wipe tube a clean. This study proposes a measurement of dynamic viscosity by recording the falling time of a sphere ball from static to passing a certain distance.
The falling ball viscometer requires the measurement of a sphere s terminal velocity, usually by measuring the time required for sphere to fall a given distance. This can be further improved by using a patented v plate, which increases the number of rotations to distance traveled, allowing smaller, more portable devices. Pdf to reduce the uncertainties in measurements obtained by means of capillary viscometers, we developed an absolute falling ball. Falling ball viscometers the falling ball viscometer is based on stokes law, and is what we will use in this laboratory investigation. Several studies on the falling ball viscometers were conducted with newtonian fluids3, and wealthy fluids in suspended particles 4. Falling ball viscometer aim the purpose of this experiment. The viscometer is meant to approximate an infinitely long column of infinite diameter. Viscometers measuring a critical physical property.
A novel handheld viscometer applicable for pointofcare. Issn 20351755, this version is available at strathprints is designed to allow users to access the research output of the university of strathclyde. The settling sphere method is applied by a permanent magnet that is released at the top of the vessel. When the sphere is dropped, the sphere experiences three forces. The ball drop device has also been applied to measure dynamic viscosity of non newtonian fluids, by varying the size and density of the balls used 8. Ulbrecht with 3 figures and i table received march 9, 1971 d sphere diameter, cm dc container diameter, cm f 16d as pg drag force on sphere, dynes. Next using the digital scales, find the mass of the teflon sphere to the nearest 0. This type of viscometer consists of a circular cylinder containing the fluid and a smooth ball. The principle of the viscometer is to determine the falling time of a sphere with known density and diameter within a fluid filled inside glass tube. This viscometer makes use of the principles in case of flow around a small sphere. An exception to this rule is the hoeppler viscometer, a falling ball instrument which states an inclination angle of exactly 80.
For commercial falling ball viscometers with sets of calibrated spheres, the constants in equation 6 are combined with the apparative factors to form the spherical constant k. It is based on stokess law, which describes the flow of a fluid past a sphere in a vertical tube, where the flow is very slow. Units of viscosity viscometer types capillary viscometers falling body methods oscillating method ultrasonic methods 30. Exploring characteristics for optimal accuracy of a settling. Us20160528a1 fallingpiston viscometer and methods for. A falling sphere viscometer is one of the simpler types of viscometers. The falling ball viscometer is one of the practical applications of either eqn. The theory is based on stokes law and is only valid. The increase in uncertainty throughout the viscosity scale being the principal disadvantage of capillary viscometry, an absolute fallingball viscometer has been.
After falling su ciently the spheres acquire terminal velocity. However, the method of a falling ball through a fluid can use common lab equipment and. In the falling ball viscometer, a spherical steel ball is allowed to fall through a tube containing the solution to be measured. Measurements of fluid viscosity using a miniature ball drop device. Since the viscometer constant is known, the kinematic viscosity of any fluid within the appropriate range for the viscometer can be found 0. If correctly selected, it reaches terminal velocity, which can be measured by the time it takes to pass two marks on the tube. A sphere of known size and density is allowed to descend through the liquid. The viscometer in the viscosity control system 100 is a falling piston viscometer 200. Ng sphere viscometer case of a sphere approaching an infinite rigid plane such as the bottom of the containing vessel of a falling sphere visco. A solid cylinder of radius r1 and length l falls under the influence of gravity through the test. Viscosity of newtonian fluids using haake falling ball viscometer.
You can now use these two numbers to determine the density of the teflon sphere gcm 3. Equation14is the basis of the falling sphere viscometer. The hoeppler principle fritz hoppler, 1897 1955, german chemist, who designed this falling ball viscometer in 1933 7 conforms to din 53015 and iso 12058. More sophisticated are vibrational viscometers used in process industries, and rotational viscometers.
The time taken for the falling sphere, whose density and radius are known, to move between two markings is measured, and then users can calculate viscosity. Viscometer uses the simple but precise hoppler principle to measure the viscosity of newtonian liquids by measuring the time. Measurement of viscosity in a vertical falling ball viscometer. For laminar flow vd2 1 in which d is the diameter of the sphere. Viscometers measuring a critical physical property lab. Pdf, measure liquid viscosity by tracking falling ball. This can be further improved by using a patented v plate, which increases the number of rotations to distance traveled, allowing smaller, more. Spe 121575 viscometer for opaque, sealed microemulsion samples. Brookfield has been considered the world standard in viscosity measurement and control for more than 85 years. The falling ball viscometer corresponds to the requirements of many international standards, i. A falling sphere viscometer is a device used to measure the viscosity of a fluid by measuring the time required for a spherical ball to fall a certain distance under gravity through a tube filled with the fluid whose viscosity is to be determined. Eventually, both forces are equal and the sphere falls with constant velocity v 1, which is obtained by equating12and. The forces acting on a sphere falling in a falling ball viscometer consist of force due to gravity f g, force due to the buoyancy of the solution f b, and force due to drag on the ball from the liquid f d. Schaschke, carl 2010 high pressure viscosity measurement.
A rigid solid sphere, with di cording to the terminal velocity of the falling ball applies ameter d and density. Small metallic spheres are dropped in to the liquid from the top. Falling ball viscometersthe falling ball viscometer is based on stokes law, and is what we will use in this laboratory investigation. Estimation of viscosity with a falling cylinder viscometer you are assigned to design a falling cylinder viscometer to measure the viscosity of newtonian liquids. Falling speed of a 2 mm ceramics ball in a 350oil batch 2 at 19. Stokes law is the basis of the falling sphere viscometer, in which the fluid is stationary in a vertical glass tube. Apr 27, 2015 falling sphere viscometer the falling ball viscometer is based on stokes law. Then, authors utilize a numerical program with an iteration scheme to. The buoyant weight of the sphere is balanced by the fluid resistance and the sphere falls with a constant velocity. Pdf design of a high precision fallingball viscometer c. A liquid is allowed to flow through its capillary tube between two etched marks and the time of flow of the liquid is measured using a stopwatch.
Virtual lab of physics falling sphere viscosimeter youtube. And to celebrate the 200th anniversary of george gabriel stokes birth i propose using the time of fall of a sphere through a fluid for a sculptural clocka public kinetic artwork that will tell the time. Viscometer c is the classical instrument for viscosity. The viscosity of a liquid can be measured using a viscometer. This type of viscometer is used for measuring newtonian fluids. Falling ball viscometers determine the viscosity of a newtonian fluid by measuring the velocity of a ball moving through the fluid. Spe 121575 viscometer for opaque, sealed microemulsion. A modification of the straight falling sphere viscometer is a rollingball viscometer, which times a ball rolling down a slope whilst immersed in the test fluid. A falling sphere viscometer with four, ringshaped, inductive proximity sensors is employed in this study. In this experiment, we measure the position of a sphere as a function of time and determine the steady state settling velocity. The falling ball viscometer is based on the measuring principle by hoppler for simple but precise dynamic viscosity measurement of transparent newtonian fluids. Measure the time with the help of stop watch that sphere takes to fall 305 mm as marked by the pieces of masking tape. A constructed inductor coil for the purpose of metal detection. R viscosity measurements with the falling ball viscometer 1.
Stokes law, viscometry, and the stokes falling sphere. Extrapolation procedures for zero shear viscosity with a falling sphere viscometer notation by v. Design of a high precision fallingball viscometer aip publishing. Allow 10 minutes for viscometer to reach equilibrium at 100f 38c or 15 min at 210f 98. Another method of measuring the viscosity of a fluid is the rotating viscometer figure 4. Falling sphere viscometer simulation example ansys courses. The friction or the deformation drag f d of the sphere moving at a constant velocity v through a fluid of infinite extend is. Viscosity of newtonian fluids using haake falling ball. Falling sphere viscometer helps you to record a specified point by dropping a fluid sample through it. Pdf design of a high precision falling ball viscometer. Falling sphere viscometer an engine oil company is using a new falling sphere viscometer to test a new range of lubricants they have been developing. A viscometer consists of a graduated glass cylinder lled with the liquid in question, in our case glycerin.
Hold one sphere, with the help of pillers, approximate 25 mm lower the glycerol surface in the cent er of the cylinder. A high precision fallingball viscometer using a fast camera arxiv. The falling sphere viscometer experiences similar problems to the capillary viscometer, as it relies on visual cues, it cannot use opaque fluids. Determination of viscosity of organic solvents theory. Developing fallingball viscometer for highly flowable. This type of viscometer consists of a circular cylinder containing the fluid and a. A standard ball is allowed to fall down this tube over a calibrated distance of 100 mm. The forces acting on a sphere falling in a falling ball viscometer consist of force due to gravity f g, force due to the buoyancy of the solution f. Falling ball viscometer principle instrumentation tools. Pdf measurement of viscosity in a vertical falling ball. A falling sphere viscometer available in an undergraduate physics laboratory. This tube carries two ring marks a and b, which are spaced 100 mm apart and which limit. Stokes law is the basis of the falling sphere viscometer, in which the fluid is stationary in a vertical transparent tube. In an ostwald viscometer the measured distance the liquid travels, l, will be always a constant.
695 49 1292 85 560 797 1526 1077 855 1143 1336 1365 552 1394 1157 1192 1179 161 1539 808 1241 792 21 1454 246 459 47 861 1571 828