Chapter Two
Theory
2.1 Viscosity
Viscosity is the tendency of a fluid to resist flow and can be thought of as the internal friction of a fluid. Microscopically, viscosity is related to molecular diffusion and depends on the interactions between molecules or, in complex fluids, larger-scale flow units. The opposite of the viscosity is the fluidity which measures the mobility for fluid layers (Secco et al, 2013). Viscosity is affected by the temperature and composition of the fluid and, for compressible fluid, also by pressure (Serway et al, 2012).
The shear viscosity of a fluid can be expressed in two distinct forms: The dynamic viscosity
The dynamic viscosity is defined as the ratio of shear stress (force over cross section area) to the rate
…show more content…
Kinematic viscosity
The kinematic viscosity is the ratio of viscosity ƞ to density ρ (taken at the same temperature and pressure). μ=ƞ/ρ (2.1.2) kinematic viscosity is normally expressed in terms of centistokes, ρ is mass density in gm/〖cm〗^3 (Druk et al,
…show more content…
Can be calculated dynamic viscosity ƞ from the kinematic viscosity μ and the density ρ according to equation (2.1.2).
The viscosity of pure liquids affects on temperature, pressure, density, and surface tension (Dutt et al, 2007). When the temperature drops the particles slow down and come closer together, the forces of attraction between them will increase and so make it harder for them to flow past each other. Thus, Dynamic viscosity of liquids increases with decreasing temperature (Binder et al, 2007). Dynamic Viscosity of Mixtures
The behavior of the viscosity is like pure liquids far from the critical point of a binary liquid mixture, Around the critical point the situation becomes more complicated (Yusur Kittany, 2014). The mode coupling theory is used to study the critical anomaly of the shear viscosity and the coefficients.
Shear Viscosity Near the Critical
They just forgot to mention the other effects of fluids in nature. “The influence of the fluid on a body moving through it depends not only on the body’s velocity but also on the velocity of the fluid,” this is called relative velocity ( ). The relative velocity of a body in a fluid has an effect on the magnitude of the acting forces. For example, as a long distance runner is running into a head wind, the force of the fluid is very strong. If the runner is running with the help of a tail wind, the current’s force is reduced and may even be unnoticeable.
Every time the container the substance is in is opened some of it will evaporate, causing the temperature of the liquid to change. As it evaporates, the temperature decreases.
At a constant temperature, a pure liquid has a vapor pressure that describes the pressure of escaped gaseous molecules that exist in equilibrium at the liquid’s surface. Adding energy to a pure liquid gives more molecules the kinetic energy to break the intermolecular forces maintaining the liquid and raises the overall temperature of the liquid. Eventually, adding energy boosts the liquid’s vapor pressure until it equals the surrounding atmospheric pressure. When this occurs, the pure liquid boils at a temperature called the boiling point.
However in my investigation, I am investigating temperature and the particle size of the solute. Prediction From using my scientific knowledge and understanding, if the particle size of the solute is smaller, the particles can easily diffuse with the solvent's particles and fill in the spaces between them. In addition, the surface area is also increased if the particle size of the solute is smaller, giving a greater area for the particles of the solvent to collide with, so the solute can dissolve quickly. If the temperature is high, more kinetic energy is given to the particles, therefore the particles would move faster, mix in with the particles of the solvent, and will easily dissolve in it. Variables inc.
The viscosity of the corn syrup, measured in seconds it takes for an iron ball to move downwards in the fluid.
In classical fluid dynamics, the Navier-Stokes equations for incompressible viscous fluids and its special (limiting) case the Euler equations for inviscid fluids are sets of non-linear partial differential equations that describes the spatiotemporal evolution of a fluid (gas). Both equations are derived from conservative principles and they model the behavior of some macroscopic variables namely: mass density, velocity and temperature.
It is the ratio of distance travelled by solute and the distance moved by solvent.
Alcohol particles break their bonds when they mix with oxygen. This is known as an exothermic reaction. Boiling points will be increased because energy is needed, bonds can be formed and broken. Breaking bonds need less energy than is needed to form bonds - an exothermic reaction. Bigger molecules use high energy to break down.
When analyzing the thermal-hydraulics of two-phase flow, it is expressed in terms of macroscopic field equations and constitutive relations using a continuous formulation. This has been incorporated in classic formulations including the homogeneous flow model, drift flux model (Zuber and Findley, 1965), and the two-fluid model (Ishii, 1975). The formulation considered the most accurate is the two-fluid model developed by Ishii due to its treatment of the interfacial interaction terms. It considers the phases separately in terms of two sets of equations that govern the mass, momentum and energy. These equations represent the macroscopic field of each phase, and are not independent of each other but have phase interaction terms that couple the transp...
Slime, has a different viscosity, based on the amount of strength you apply when playing with it. Slowly placing your hands on the slime is being described as a small amount of weight being applied to the slime, they will feel thin and water-like, letting you sink your hand into the jelly like substance. Punching it, or throwing it against a wall,
where p is the density of the fluid (in runner’s case: air); v is the velocity of the runner; A is the cross-sectional area perpendicular to the runner’s velocity; and D is the dimensionless quantity called the drag coefficient.
- the effect of Viscosity on liquid flow (turbulent/laminar) I have consulted my teachers for guidance and I have also looked very carefully into the "the Suggestions papers" which contain many possible investigations which have been done in the past. I opted to choose neither of them but many aspects I will be looking into in my investigation are similar to those in the papers.
Surface Tension: The contractive tendency of a liquid that allows it to resist an external force. This is measured in Newton.
It is defined as” an increase in volume of the mass due to suction of water or due to contact of water for a longer
k.e. = 1/2pv^3At, where A is the area of the surface and t is the time.