Fluid dynamics - wk 7

What is a fluid?

A fluid is a substance that continually deforms or flows under an applied force or shear stress.

What are the different types of fluids?

Fluids can be classified as liquids, gases, plasmas, and plastic solids.

What is viscosity?

Viscosity is a measure of how thick a fluid is and how easily it flows.

What is equilibrium in the context of fluid pressure?

Equilibrium occurs when static pressure, hydrostatic pressure, and dynamic pressure are constant.

Explain laminar flow.

Laminar flow is streamlined and occurs in parallel thin layers with no disruption between them.

Explain turbulent flow.

Turbulent flow is chaotic and has constant changes in direction, often causing fluctuations in pressure.

What is Bernoulli's Principle?

Bernoulli's Principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in internal pressure.

What is Reynolds number?

Reynolds number is a dimensionless number used to predict flow patterns in different fluid flow situations.

What does a low Reynolds number indicate?

A low Reynolds number indicates laminar flow, characterized by low velocity, narrow pipes, and high viscosity.

What does a high Reynolds number indicate?

A high Reynolds number indicates turbulent flow, characterized by high velocity, large diameters, and low viscosity.

What factors affect blood viscosity?

Blood viscosity is affected by temperature, the volume of red blood cells, clotting factors, and the orientation of blood cells.

How does an increase in viscosity affect blood flow?

An increase in viscosity results in higher resistance to flow, slowing down the movement of blood.

Define the volumetric flow rate.

Volumetric flow rate is the volume of liquid that passes through a sectional area per unit time, typically expressed in cubic meters per second.

What is static pressure?

Static pressure is the pressure exerted by a fluid at rest or when it is not flowing.

What is hydrostatic pressure?

Hydrostatic pressure is the pressure exerted by the weight of a fluid above a point in the fluid.

What is dynamic pressure?

Dynamic pressure is the pressure associated with the motion of a fluid, directly related to its velocity.

How is blood pressure measured?

Blood pressure is measured using a cuff that applies pressure to the artery and detects the flow through sound (Korotkoff sounds).

What is the relationship between flow rate and vessel diameter?

As the diameter of a vessel decreases, the flow rate increases if the pressure remains constant.

Define hydrostatic pressure equation.

Hydrostatic pressure is calculated using the formula P = h * ρ * g, where h is height, ρ is density, and g is gravity.

What effects does vessel constriction have on blood flow?

Constriction increases blood velocity and can lead to turbulence on the other side of the constricted area.

What happens to blood flow through capillaries?

Blood flow in capillaries tends to be laminar due to their small diameter and slow speed.

What clinical implications does turbulent flow have?

Turbulent flow can indicate blockages or abnormalities in blood vessels, often associated with conditions like arteriosclerosis.

What is the impact of temperature on blood flow?

Lower temperatures increase blood viscosity, reducing blood flow, especially in the extremities.

In what conditions does the heart pump more blood?

The heart pumps more blood during exercise due to increased demand for oxygen and nutrients.

What do higher systolic numbers indicate in blood pressure readings?

Higher systolic numbers indicate higher pressure in the arteries during heart contractions.

What does diastolic pressure represent?

Diastolic pressure reflects the pressure in the arteries when the heart is at rest between beats.

What is arteriosclerosis?

Arteriosclerosis is the thickening and hardening of artery walls, which can affect blood flow.

What is the consequence of atherosclerosis on blood vessels?

Atherosclerosis can lead to narrowed arteries, increased turbulence, and higher risk of blockages.

Explain the importance of knowing the Reynolds number.

Knowing the Reynolds number helps predict whether blood flow will be laminar or turbulent, which is critical for diagnosing vascular issues.

How does blood viscosity change during certain conditions?

Blood viscosity can increase with dehydration, increasing resistance to flow.

Describe Poiseuille’s law.

Poiseuille’s law states that flow rate is proportional to the pressure gradient and the radius of the tube, and inversely proportional to the viscosity.

What does turbulent flow lead to in the context of arterial health?

Turbulent flow leads to increased pressure on arterial walls, heightening the risk of aneurysms and blockages.

Define non-Newtonian fluids. Give an example.

Non-Newtonian fluids have variable viscosity based on the stress applied; an example is ketchup.

Define Newtonian fluids. Give an example.

Newtonian fluids have constant viscosity regardless of applied stress; an example is water.

What happens when blood pressure is consistently high?

Consistently high blood pressure can weaken blood vessel walls and lead to serious health issues such as heart attack or stroke.

What is the effect of high altitude on blood flow?

High altitude can lead to lower oxygen levels in the blood and may cause changes in blood viscosity and flow.

How do exercise and dynamic activity affect blood flow?

Exercise increases heart rate and cardiac output, enhancing blood flow to muscles and organs.

What is the role of the vascular system in health?

The vascular system is responsible for transporting blood, nutrients, oxygen, and waste products throughout the body.

What can cause variations in blood pressure?

Blood pressure can be affected by factors such as age, stress, physical activity, medication, and underlying health conditions.

Explain what is meant by the term 'shear stress' in fluids.

Shear stress in fluids refers to the force per unit area exerted by the fluid layers sliding past each other.

What clinical conditions can turbulent flow indicate?

Turbulent flow can indicate vascular blockages, congenital heart defects, or abnormalities in blood vessel structure.

What does a measurement of blood pressure between 120 to 140 systolic indicate?

It indicates a pre-hypertensive condition, requiring monitoring and lifestyle modifications.

What is the relationship between fluid density and flow rate?

Higher fluid density typically increases resistance and affects the flow rate, making it slower.

What effect does lowering the diameter of a blood vessel have on flow?

Lowering the diameter of a blood vessel increases flow velocity but can also increase resistance and lead to turbulence.

How does the cardiovascular system respond during physical stress?

The cardiovascular system increases heart rate and blood flow to ensure adequate oxygen delivery and nutrient supply to muscles.

What happens to blood flow in compromised vessels?

In compromised vessels, blood flow can become turbulent, leading to possible complications such as clots or reduced circulation.

What is laminar flow?

Laminar flow is a smooth, streamlined movement of fluid where parallel layers slide easily over each other with no disruption.

Characteristics of laminar flow

1. Smooth, regular paths; 2. Layers slide easily; 3. Occurs at low flow rates; 4. High viscosity increases chances of laminar flow.

Examples of laminar flow

1. Blood flow in capillaries; 2. Injections; 3. Anesthesia gas flow.

What is turbulent flow?

Turbulent flow is chaotic and irregular movement of fluid, characterized by fluctuations in velocity and pressure.

Characteristics of turbulent flow

1. Constantly changing direction; 2. Mixing between layers; 3. Often occurs in blocked vessels or aneurysms.

Flow equation by Poiseuille

Flow is the difference in pressure between two points in a tube divided by resistance.

Factors affecting laminar flow

1. Pressure difference; 2. Tube radius; 3. Liquid density; 4. Tube length.

What is the Reynolds number?

Reynolds number is a dimensionless quantity that predicts whether flow will be laminar or turbulent. It is the ratio of inertial forces to viscous forces in a fluid.

What affects the Reynolds number?

Reynolds number is affected by fluid velocity, diameter, and viscosity: high velocity and diameter with low viscosity yield a high Reynolds number (turbulent flow).

Conditions for low Reynolds number

To achieve a low Reynolds number (laminar flow), you need low velocity, small diameter, high viscosity, and low density in the fluid.

Reynolds number thresholds

1. Laminar flow: Reynolds number < 2000; 2. Transitional flow: Reynolds number 2000-4000; 3. Turbulent flow: Reynolds number > 4000.

Why is low viscosity important for laminar flow?

Low viscosity allows fluids to flow smoothly with less resistance, adhering to laminar flow characteristics.

Impact of exercise on Reynolds number

During exercise, Reynolds numbers decrease, leading to less turbulent blood flow compared to resting states.

Where can turbulent flow be observed in the body?

Turbulent flow can be seen in the arch of the aorta, particularly in cases of congenital heart defects and conditions like stenosis and aneurysms.

What causes turbulence in blood flow?

Turbulence can occur due to stenosis (narrowing of arteries) caused by plaque build-up, stiff valves, or conditions like aneurysms, resulting in high pressure on arterial walls.

Where is turbulent flow commonly found in the body?

Turbulent flow is often found at the arch of the aorta, the base of the pulmonary artery, and in the descending aorta, especially in athletes and individuals with congenital heart defects.

Impact of constriction on blood flow

Constricted blood vessels lead to laminar flow before the constriction and turbulent flow afterwards, resulting in increased pressure and potential complications like aneurysms.

How does blood pressure relate to blood flow?

In blood pressure measurement, laminar flow creates no sound; as pressure is applied and flow becomes turbulent, Korotkoff sounds are heard, indicating systolic and diastolic pressures.

What are Korotkoff sounds?

Korotkoff sounds are the noises heard through a stethoscope when measuring blood pressure, caused by turbulent blood flow in response to pressure changes from a sphygmomanometer.

How does the anatomy of blood vessels affect flow?

The diameter and condition of blood vessels (e.g., presence of plaque or plaque narrowing) significantly influence whether blood flow is laminar or turbulent, impacting blood pressure and overall circulatory health.

What happens to cerebral spinal fluid flow with cervical spine misalignment?

Misalignment in the cervical spine can lead to turbulent flow in the cerebral spinal fluid, potentially causing headaches and contributing to neurodegenerative conditions like multiple sclerosis.

What is considered high blood pressure?

High blood pressure is defined as anything over 140/90 mmHg; pre-hypertension is between 120/80 and 140/90 mmHg.

Common causes of high blood pressure

Factors affecting high blood pressure include genetics, lifestyle, heart defects, kidney disease, drugs, and endocrine problems.

What is hypotension?

Hypotension is abnormally low blood pressure, often caused by dehydration or anemia, and is usually less concerning than high blood pressure.

What should you do before measuring blood pressure?

Measure blood pressure after lying down for at least 15 minutes and always discard the first reading as it may be variable.

What does a high systolic and low diastolic pressure indicate?

A high systolic and low diastolic pressure may indicate a significant drop in pressure through the system, which could be genetic or pathological.

How does blood pressure change with age?

Blood pressure tends to increase with age, which can increase the risk of vascular issues and other health problems.

Summary of fluid dynamics topics covered

We covered fluid properties, density, velocity, flow rate, viscosity, ideal vs. real fluids, Newtonian vs. non-Newtonian fluids, pressure factors, Bernoulli's principle, blood pressure, laminar/turbulent flow, and Reynolds numbers.

What are ideal fluids?

Ideal fluids are hypothetical fluids that are incompressible and have no viscosity, allowing for smooth, uninterrupted flow without any energy loss.

What are real fluids?

Real fluids are those that exist in the real world and have viscosity, experiencing resistance to flow and energy loss due to internal friction.

What are Newtonian fluids?

Newtonian fluids are fluids whose viscosity remains constant regardless of the stress applied to them, such as water and air.

What are non-Newtonian fluids?

Non-Newtonian fluids have a variable viscosity that changes with the applied stress or shear rate, such as ketchup or blood.

Example of a Newtonian fluid

Water is a classic example of a Newtonian fluid, maintaining a consistent viscosity under varying flow conditions.

Example of a non-Newtonian fluid

Ketchup is an example of a non-Newtonian fluid that becomes less viscous when shaken or forced, allowing it to flow more easily.

How does shear rate affect non-Newtonian fluids?

In non-Newtonian fluids, increased shear rate can either increase or decrease viscosity, leading to behaviors such as shear thinning or shear thickening.

What happens when you use the cuff on the brachial artery during blood pressure measurement?

The cuff applies pressure on the brachial artery, leading to laminar flow and no sounds when the cuff pressure is lower than systolic pressure.

What are Korotkoff sounds?

Korotkoff sounds are the noises arising from turbulent blood flow in the artery that are observed when measuring blood pressure.

What does the first sound heard during blood pressure measurement indicate?

The first sound indicates systolic pressure as more pressure is released from the cuff, leading to turbulent flow.

What occurs as pressure in the cuff continues to decrease after the systolic pressure is detected?

As pressure continues to decrease, turbulent flow persists until diastolic pressure is reached, at which point no sound is heard.

When is diastolic pressure determined during blood pressure measurement?

Diastolic pressure is determined when the cuff pressure is equal to the normal blood pressure and no sounds are heard.