Application of Non-Newtonian fluid

 

Speed bump: Application of Non-Newtonian Fluid

 

What is Fluid?

A Fluid is a liquid, gas, or other material that continuously deform (flows) under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear force applied to them. The different properties of fluid are viscosity, Temperature, Density, Pressure.

Types of fluid according to Viscosity Behaviour.

1.Newtonian fluid - 

The fluid which viscosity remain constant irrespective of shear applied at constant temperature.

2.Non Newtonian fluid- 

The fluid which viscosity changes with respective to shear applied. Its means it has non linear relationship between shear rate and shear stress.

Newton's law of Viscosity

It states that 'the shear stress is directly proportional to velocity gradient'.It defines the relationship between the shear stress and shear rate of a fluid subjected to a mechanical stress. The ratio of shear stress to shear rate is a constant, for a given temperature and pressure.

The behaviour of Non Newtonian fluid can be described as below-

1.Time dependent

A. Dilatant - 

A dilatant also termed shear thickening material is one in which viscosity increases with the rate of shear strain (Fig 1) Eg:-Quick sand ,cornstarch and water. Such a shear thickening fluid, also known by the initialism STF, it is an example of a non- Newtonian fluid. This behaviour is usually not observed in pure materials, but can occur in suspension depends on factors as particle size, shape, and distribution. Shear thickening behavior occurs when a colloidal suspension transitions from a stable state to a state of flocculation.    

B. Pseudoplastic -

It is also termed as shear thinning is the non-Newtonian behavior of fluids whose viscosity decreases under shear strain (Fig 1) Eg:- ketchup, and nail polish.It is often observed in polymer solutions and molten polymers, as well as complex fluids and suspensions.

                                                                         

                                                                                       Figure.1: Graph viscosity- stress

2.Time independent

A. Rheopectic -

 It is Non Newtonian fluid whose viscosity is time dependent  the longer the fluid undergoes shearing force, the higher its viscosity. These fluid exhibits a reversible decrease in shear stress with time at constant shear rate.  Eg:-gypsum pastes, printer inks      

B. Thixotropic -

Its opposite of Rheopectic fluid whose viscosity is time dependent  the longer the fluid undergoes shearing, the its viscosity decrease and takes time to come in original state at static condition.Eg:- Paint, Cosmetic glue.

    

                                                                               Figure.2: Graph of viscosity- stress

·        Problem statement :- With passing decade the problems are rising with increase in height of speed bump with 3- 4 inch to reduce speed of vehicle. This lead to spinal damage, rupture of vehicles due to Inconsistent speed,slowing down emergency vehicles.

·         

Modern solution :

The speed bump structure need to develop. The one of the best solution is application of non-Newtonian fluid (oobleck) in structure. The non-Newtonian fluid speed breaker’s reduces the rigidity to make it easier for vehicles to pass without bouncing or jumping.

Working principle :

 

The speed bump with construction of non-Newtonian fluid works on principle "deformation of fluid under stress".Two rubber products are pre-shaped to standard sizes to meet industry standards.Then they are bolted down for installation The viscosity changes with intensity of shear force.Depend on passing vehicles speed through it, it will deform naturally with pressure of vehcile.So that the vehicle is stable and excessive to reduce turbulence.

Design of speed bump :-

Figure.3: Structure of Speed bump

• Speed breakers are basically in 3.7-meter width and having a height of 0.7 meter and advisory crossing speed of 25 km/hr.,

1.Packaging material  :

As this model relates to public safety, the packing material for the Oobleck combination should have high grade properties. Some of the expected properties are highly insulating and minimal chemical reactivity. Kevlar and Nanocellulose, are two well-known materials that meet the criteria for the necessary qualities. Braided carbon fibre tubes are an affordable alternative that can be used. They serve to contain the mixing of non-Newtonian fluid.

Required properties of packaging material:-

• High tensile strength, stiffness 
• Low chemical reactivity, so doesn’t react with Oobleck. 
• High cut resistance 
• No thermal shrinkage 
• Low thermal conductivity, so no heat transfer between inner fluid and surrounding environment.

Figure.4: Packaging tubes

2.Channel section material: 

The packaging tubes need to be housed in a conduit which enables the controlled flow of fluid in and out of the chamber into the reservoir when the wheels of the automobile pass over the speed bump.Synthetic rubber material is suited for this purpose because it displays the following properties: 

• Great Elasticity 
• Electrically insulated material 
• Good abrasion resistance.

Figure.5: Synthetic rubber

3.Outer shell: 

PVC coated polyester textiles are an option for the outer shell material. Base fabric, adhesive or prime coat, external coatings , and top coating systems make up these architectural fabrics. PVC coated polyester has a fine texture on the front and a smooth poly-vinyl coating on the back. Since vehciles are anticipated to drive over this shell, PVC polyester fits the essential requirement of having a high tensile strength. It resists tearing and ripping readily and is waterproof. The coating applied to this vinyl contains UV stabilisers, anti-fungicides, and fire retardant chemicals.

Figure.6: PVC polyester

4.Base plate :-

The structure need to be lightweight and transportable, so the base plate includes fastening holes for its mounting with bolts and screws. The material that perfectly serves the purpose is fiber reinforced composite plastic panels. In the speed breaker system the speed breaker is made up of mild steel strips (8mm thick). The dome is speed breaker is welded with the frame which is rectangular in shape and made of 3 mm angle iron. Made of mild steel sheets of 6 mm thickness according to IRC.  

Figure.7: Base Plate

5. Non Newtonian fluid "oobleck"-

Oobleck is defined as the mixture of cornstarch and water in the ratio of 1:1.25 and at this proportion only the fluid will behave the shear thickening properties. Before doing this preparation, we must do several precautions to resist the microbiological growth in the fluids are:

• The water taken are boiled above 100’C to kill the microbiological growth in a water.
• The corn starch must be oven dried before using them.

Figure.8: Oobleck

 Recent trends in speed bump with Non-Newtonian fluid 

• The current Oobleck speed bump is useful for everything except emergency vehicles. It becomes necessary for these cars to go at high speeds, which would have negative effects on them, delay the critical response time noticeably, have negative effects on the car, and ultimately harm the patient's health.
• Non-Newtonian fluid breakers are designed with an emergency vehicle detection system mounted close to the hump to address this serious problem. This system includes progressive cavity pumps and a sound signal detection unit that take the necessary actions to ensure the fluid is pumped as efficiently as possible to deflate the bump and certify a smooth path for the transport of emergency carriers.

Conclusion

• As the molecular weight of the carrier fluid rises, the viscosity of STF and the amplitude of shear thickening also rise. 
• The Non-Newtonian fluid speed breaker significantly improves the fuel efficiency of automobiles. 
• Non-Newtonian fluid speed breakers have very inexpensive installation and maintenance costs when compared to conventional speed breakers. 
• They also do not need vehicles to stop completely in front of them, which reduces traffic congestion. • If a car is driving within the speed limit, it doesn't harm the mechanical parts like the shock absorbers and steering system. •
• The configuration may be installed in an hour and is entirely portable. designed a speed hump based on the STF principle.

GUIDE:-N.V.Borse

HOME ASSIGNMENT ACTIVITY BY:

FY_ME_BATCH 1_GROUP 5

COURSE: FLUID ENGINEERING

• Himanshu Harip
• Harshal Thakur
• Nidhi Hingankar
• Swayam Jadhav
• Piyush Joshi
• Akshata Kalbhor

 Department of mechanical engineering, VIT pune