sme029 1p0434shock wave
DESCRIPTION
gelombang kejutTRANSCRIPT
Slide 1Interactive page
Slide 14
Change the narration to: ‘As the approaching shock wave hits the wedge, it undergoes reflection and diffraction’
7
1
Start with definition of shock, voice over to say that internal and
external shock will be discussed in this animation
Slide 4
Slide 4
“shock” with approaching flow, keep wedge stationary
Slide 13
throat, P1 and P2
Slides 6-13
6
Modify quiz question 1 - Change language to say “across” the shock wave
Modify quiz question 2 -Correct answer is 1, not 2, Reframe as marked and show downstream/upstream on figure
Slides 16 & 17
Fundamentals of Gas Dynamics
A shock wave is a disturbance that propagates through a medium. While the shock-wave usually travels through the medium, standing or stationary shock waves can occur in some circumstances in both liquids and gases.
*
Voice Over:
A shock wave is a disturbance that propagates through a medium. While the shock-wave usually travels through the medium, standing or stationary shock waves can occur in some circumstances in both liquids and gases.
Mach number describes the type of flow. This demo illustrates both internal and external flow patterns.
Click start.
Shock Wave
Converging Diverging Nozzle
A nozzle is often used to control the speed of flow.
Voice Over:
A nozzle is often used to control the speed of flow.
A converging-diverging nozzle has two regions - One of reducing diameter, the other of increasing diameter, separated by a “throat”.
The important parameters for a converging-diverging nozzle are its inlet pressure and the outlet pressure or back pressure.
As the ratio Pi/Pb increases, that is as the back pressure is lowered, the flow through the nozzle speeds up until it reaches Mach 1, at which point the flow gets choked. After this point the mass flow rate does not increase any more.
While the exact value of the ratio Pi/Pb at which the nozzle gets choked depends on the throat diameter, the behavior of this internal flow will be explained in detail in the next section.
Visual Guidelines:
Fade in the text.
Fade in the image without labels initially. As the narration says, ‘one of reducing diameter’ animate the nozzle shape lines with a different color till its throat. As the narration says, ‘the other of increasing diameter’ animate the nozzle shape lines from the throat to the exit section with different color. Also fade in the respective labels as shown above.
Animate the labels in sync with the narration as shown above.
*
Back Pressure (Pb):
Voice Over:
Vary the back pressure to see the flow of pattern in the nozzle.
Visual Guidelines:
Refer to the next slides for animation to be done when the cursor is moved along down the seek bar given above.
*
The flow through the nozzle is completely subsonic.
Voice Over:
The flow through the nozzle is completely subsonic that is the nozzle isn't choked.
The flow accelerates out of the chamber through the converging section, reaching its maximum subsonic speed at the throat.
The flow then decelerates through the diverging section and exhausts into the ambient as a subsonic jet.
Visual Guidelines:
*
Fundamentals of Gas Dynamics
Reference slide if the back pressure is reduced by one step
The flow pattern is exactly the same as in subsonic flow, except that the flow speed at the throat has just reached Mach 1.
Voice Over:
The flow pattern is exactly the same as in subsonic flow, except that the flow speed at the throat has just reached Mach 1.
Flow through the nozzle is now choked since further reductions in the back pressure can't move the point of M=1 away from the throat.
Visual Guidelines:
*
Fundamentals of Gas Dynamics
Reference slide if the back pressure is further reduced by one step
A region of supersonic flow forms just downstream of the throat.
Voice Over:
A region of supersonic flow forms just downstream of the throat.
Unlike a subsonic flow, the supersonic flow accelerates as the area gets bigger. This region of supersonic acceleration is terminated by a normal shock wave.
The shock wave produces a near-instantaneous deceleration of the flow to subsonic speed. This subsonic flow then decelerates through the remainder of the diverging section and exhausts as a subsonic jet.
Visual Guidelines:
*
Fundamentals of Gas Dynamics
Reference slide if the back pressure is further reduced by one step
The supersonic region extends all the way down the nozzle until the shock is sitting at the nozzle exit.
Voice Over:
The supersonic region extends all the way down the nozzle until the shock is sitting at the nozzle exit.
Because of a very long region of acceleration that is the entire nozzle length the flow speed just before the shock will be very large.
However, after the shock the flow in the jet will still be subsonic.
Visual Guidelines:
*
Fundamentals of Gas Dynamics
Reference slide if the back pressure is further reduced by one step
Shock bends out into the jet, and a complex pattern of shocks and reflections is set up in the jet which will now involve a mixture of subsonic and supersonic flow, or just supersonic flow.
Voice Over:
Shock bends out into the jet, and a complex pattern of shocks and reflections is set up in the jet which will now involve a mixture of subsonic and supersonic flow, or just supersonic flow.
Because the shock is no longer perpendicular to the flow near the nozzle walls, it deflects it inward as it leaves the exit producing an initially contracting jet.
We refer to this as overexpanded flow because in this case the pressure at the nozzle exit is lower than that in the ambient.
Visual Guidelines:
*
Fundamentals of Gas Dynamics
Reference slide if the back pressure is further reduced by one step
Waves in the jet disappear altogether, and the jet will be uniformly supersonic.
Voice Over:
Back pressure is now equal to the pressure at the nozzle exit. In this case, the waves in the jet disappear altogether, and the jet will be uniformly supersonic. This situation, since it is often desirable, is referred to as the 'design condition'.
Visual Guidelines:
*
Fundamentals of Gas Dynamics
Reference slide if the back pressure is further reduced by one step
Expansion waves form at the nozzle exit.
Voice Over:
Exit pressure is now greater than back pressure. In this situation (called 'underexpanded') what we call expansion waves (that produce gradual turning and acceleration in the jet) form at the nozzle exit.
Visual Guidelines:
*
Voice Over:
A shock wave can propagate in either a solid or a fluid. Consider an approaching shock wave hitting a stationary wedge as shown. As the approaching shock wave hits the wedge, it undergoes reflection and diffraction. Shock wave thus produced may either reflect or diffract or both. The behavior of the shock wave depends on the shape of the object and the speed of the wave.
Visual Guidelines:
Reference video file: Leighton_2331
Since in the video the shape of the object is sphere the shape of the shock wave produced after the hit is sphere. Modify the shape in this case to a wedge. Add color to indicate temperature visually. The portion of the wave near the wedge would be hot (red) & as the wave moves away from the wedge show the color changing to yellow, blue….to indicate temperature decrease.
Shock Wave
J.D. Anderson, Modern Compressible Flow with Historical Perspective, 3rd Edition, McGraw-Hill, 2003.
H.W. Liepmann and A. Roshko, Elements of Gas Dynamics, Dover Publications, 2001.
Reference Links:
Fundamentals of Gas Dynamics
The velocity, temperature and pressure across the shock wave are characterized by
Euler's Equation
Bernoulli's Equation
Navier-Stokes Equation
Rankine-Hugoniot Equation
That’s correct.
The velocity, temperature and pressure across the shock wave are characterized by Rankine-Hugoniot Equation.
Feedback when any other option is selected:
Incorrect.
The velocity, temperature and pressure across the shock wave are characterized by Rankine-Hugoniot Equation.
Shock Wave
Pressure is higher but Temperature is lower
Pressure is lower but Temperature is higher
This image will be enhanced visually
*
That’s correct.
Downstream of the shock wave pressure and temperature are higher.
Feedback when any other option is selected:
Incorrect.
Downstream of the shock wave pressure and temperature are higher.
Visual Guidelines:
Please enhance the image given on the slide visually as done in slide 13.
Shock Wave
All thermodynamic properties of the medium change gradually
All thermodynamic properties of the medium change instantaneously
All thermodynamic properties of the medium change almost instantaneously
Some thermodynamic properties of the medium change gradually, some instantaneously
*
That’s correct.
At the shock wave-front all thermodynamic properties of the medium change almost instantaneously.
Feedback when any other option is selected:
Incorrect.
At the shock wave-front all thermodynamic properties of the medium change almost instantaneously.
Shock Wave
Fundamentals of Gas Dynamics
The strength of a shock can be measured by the ratio of downstream to upstream pressures. As the Mach number increases
the strength of the shock wave decreases
the strength of the shock wave increases
depends on the medium of propagation
depends on the initial pressure in the medium
*
That’s correct.
As the Mach number increases the strength of the shock wave increases
Feedback when any other option is selected:
Incorrect.
As the Mach number increases the strength of the shock wave increases
Shock Wave
cavitations caused by the collapse of a bubble
objects such as bullets or planes flying faster than sound
explosions in gaseous media
*
That’s correct.
Feedback when options 1 or 2 or 3 is/are selected:
Partially correct.
Incorrect.
Slide 14
Change the narration to: ‘As the approaching shock wave hits the wedge, it undergoes reflection and diffraction’
7
1
Start with definition of shock, voice over to say that internal and
external shock will be discussed in this animation
Slide 4
Slide 4
“shock” with approaching flow, keep wedge stationary
Slide 13
throat, P1 and P2
Slides 6-13
6
Modify quiz question 1 - Change language to say “across” the shock wave
Modify quiz question 2 -Correct answer is 1, not 2, Reframe as marked and show downstream/upstream on figure
Slides 16 & 17
Fundamentals of Gas Dynamics
A shock wave is a disturbance that propagates through a medium. While the shock-wave usually travels through the medium, standing or stationary shock waves can occur in some circumstances in both liquids and gases.
*
Voice Over:
A shock wave is a disturbance that propagates through a medium. While the shock-wave usually travels through the medium, standing or stationary shock waves can occur in some circumstances in both liquids and gases.
Mach number describes the type of flow. This demo illustrates both internal and external flow patterns.
Click start.
Shock Wave
Converging Diverging Nozzle
A nozzle is often used to control the speed of flow.
Voice Over:
A nozzle is often used to control the speed of flow.
A converging-diverging nozzle has two regions - One of reducing diameter, the other of increasing diameter, separated by a “throat”.
The important parameters for a converging-diverging nozzle are its inlet pressure and the outlet pressure or back pressure.
As the ratio Pi/Pb increases, that is as the back pressure is lowered, the flow through the nozzle speeds up until it reaches Mach 1, at which point the flow gets choked. After this point the mass flow rate does not increase any more.
While the exact value of the ratio Pi/Pb at which the nozzle gets choked depends on the throat diameter, the behavior of this internal flow will be explained in detail in the next section.
Visual Guidelines:
Fade in the text.
Fade in the image without labels initially. As the narration says, ‘one of reducing diameter’ animate the nozzle shape lines with a different color till its throat. As the narration says, ‘the other of increasing diameter’ animate the nozzle shape lines from the throat to the exit section with different color. Also fade in the respective labels as shown above.
Animate the labels in sync with the narration as shown above.
*
Back Pressure (Pb):
Voice Over:
Vary the back pressure to see the flow of pattern in the nozzle.
Visual Guidelines:
Refer to the next slides for animation to be done when the cursor is moved along down the seek bar given above.
*
The flow through the nozzle is completely subsonic.
Voice Over:
The flow through the nozzle is completely subsonic that is the nozzle isn't choked.
The flow accelerates out of the chamber through the converging section, reaching its maximum subsonic speed at the throat.
The flow then decelerates through the diverging section and exhausts into the ambient as a subsonic jet.
Visual Guidelines:
*
Fundamentals of Gas Dynamics
Reference slide if the back pressure is reduced by one step
The flow pattern is exactly the same as in subsonic flow, except that the flow speed at the throat has just reached Mach 1.
Voice Over:
The flow pattern is exactly the same as in subsonic flow, except that the flow speed at the throat has just reached Mach 1.
Flow through the nozzle is now choked since further reductions in the back pressure can't move the point of M=1 away from the throat.
Visual Guidelines:
*
Fundamentals of Gas Dynamics
Reference slide if the back pressure is further reduced by one step
A region of supersonic flow forms just downstream of the throat.
Voice Over:
A region of supersonic flow forms just downstream of the throat.
Unlike a subsonic flow, the supersonic flow accelerates as the area gets bigger. This region of supersonic acceleration is terminated by a normal shock wave.
The shock wave produces a near-instantaneous deceleration of the flow to subsonic speed. This subsonic flow then decelerates through the remainder of the diverging section and exhausts as a subsonic jet.
Visual Guidelines:
*
Fundamentals of Gas Dynamics
Reference slide if the back pressure is further reduced by one step
The supersonic region extends all the way down the nozzle until the shock is sitting at the nozzle exit.
Voice Over:
The supersonic region extends all the way down the nozzle until the shock is sitting at the nozzle exit.
Because of a very long region of acceleration that is the entire nozzle length the flow speed just before the shock will be very large.
However, after the shock the flow in the jet will still be subsonic.
Visual Guidelines:
*
Fundamentals of Gas Dynamics
Reference slide if the back pressure is further reduced by one step
Shock bends out into the jet, and a complex pattern of shocks and reflections is set up in the jet which will now involve a mixture of subsonic and supersonic flow, or just supersonic flow.
Voice Over:
Shock bends out into the jet, and a complex pattern of shocks and reflections is set up in the jet which will now involve a mixture of subsonic and supersonic flow, or just supersonic flow.
Because the shock is no longer perpendicular to the flow near the nozzle walls, it deflects it inward as it leaves the exit producing an initially contracting jet.
We refer to this as overexpanded flow because in this case the pressure at the nozzle exit is lower than that in the ambient.
Visual Guidelines:
*
Fundamentals of Gas Dynamics
Reference slide if the back pressure is further reduced by one step
Waves in the jet disappear altogether, and the jet will be uniformly supersonic.
Voice Over:
Back pressure is now equal to the pressure at the nozzle exit. In this case, the waves in the jet disappear altogether, and the jet will be uniformly supersonic. This situation, since it is often desirable, is referred to as the 'design condition'.
Visual Guidelines:
*
Fundamentals of Gas Dynamics
Reference slide if the back pressure is further reduced by one step
Expansion waves form at the nozzle exit.
Voice Over:
Exit pressure is now greater than back pressure. In this situation (called 'underexpanded') what we call expansion waves (that produce gradual turning and acceleration in the jet) form at the nozzle exit.
Visual Guidelines:
*
Voice Over:
A shock wave can propagate in either a solid or a fluid. Consider an approaching shock wave hitting a stationary wedge as shown. As the approaching shock wave hits the wedge, it undergoes reflection and diffraction. Shock wave thus produced may either reflect or diffract or both. The behavior of the shock wave depends on the shape of the object and the speed of the wave.
Visual Guidelines:
Reference video file: Leighton_2331
Since in the video the shape of the object is sphere the shape of the shock wave produced after the hit is sphere. Modify the shape in this case to a wedge. Add color to indicate temperature visually. The portion of the wave near the wedge would be hot (red) & as the wave moves away from the wedge show the color changing to yellow, blue….to indicate temperature decrease.
Shock Wave
J.D. Anderson, Modern Compressible Flow with Historical Perspective, 3rd Edition, McGraw-Hill, 2003.
H.W. Liepmann and A. Roshko, Elements of Gas Dynamics, Dover Publications, 2001.
Reference Links:
Fundamentals of Gas Dynamics
The velocity, temperature and pressure across the shock wave are characterized by
Euler's Equation
Bernoulli's Equation
Navier-Stokes Equation
Rankine-Hugoniot Equation
That’s correct.
The velocity, temperature and pressure across the shock wave are characterized by Rankine-Hugoniot Equation.
Feedback when any other option is selected:
Incorrect.
The velocity, temperature and pressure across the shock wave are characterized by Rankine-Hugoniot Equation.
Shock Wave
Pressure is higher but Temperature is lower
Pressure is lower but Temperature is higher
This image will be enhanced visually
*
That’s correct.
Downstream of the shock wave pressure and temperature are higher.
Feedback when any other option is selected:
Incorrect.
Downstream of the shock wave pressure and temperature are higher.
Visual Guidelines:
Please enhance the image given on the slide visually as done in slide 13.
Shock Wave
All thermodynamic properties of the medium change gradually
All thermodynamic properties of the medium change instantaneously
All thermodynamic properties of the medium change almost instantaneously
Some thermodynamic properties of the medium change gradually, some instantaneously
*
That’s correct.
At the shock wave-front all thermodynamic properties of the medium change almost instantaneously.
Feedback when any other option is selected:
Incorrect.
At the shock wave-front all thermodynamic properties of the medium change almost instantaneously.
Shock Wave
Fundamentals of Gas Dynamics
The strength of a shock can be measured by the ratio of downstream to upstream pressures. As the Mach number increases
the strength of the shock wave decreases
the strength of the shock wave increases
depends on the medium of propagation
depends on the initial pressure in the medium
*
That’s correct.
As the Mach number increases the strength of the shock wave increases
Feedback when any other option is selected:
Incorrect.
As the Mach number increases the strength of the shock wave increases
Shock Wave
cavitations caused by the collapse of a bubble
objects such as bullets or planes flying faster than sound
explosions in gaseous media
*
That’s correct.
Feedback when options 1 or 2 or 3 is/are selected:
Partially correct.
Incorrect.