Theories Discussion > Katabatic wind
The wind plays its own music
Star man:
I have completed some simple calculations of wind force on the tent. I have used a formular that is used to estimate the wind loading on civil structures. I had broken it down into detail, but for some reason all my text has just vanished so here is the simple version:
F= AxPxCd
A is cross sectional area normal to wind direction
P is the wind pressure = 0.613 x V^2. V is I metres per second
Cd is the drag coefficient which is about 1.4 for a smallish rectangle
At 100 miles per hour the force on the tent would be about 870kg
At 80 miles per hour it would be about 620 Kg
Most of this force would be spread out across th fabric on the side exposed to the wind and also taken up by the tension in the rope and then transmitted to the supports that the rope is attached to.
All in all it doesn't seem that significant. For 100 miles per hour it may have been approaching the limit for the rope but probably not for the tent fabric. If there was a weak point (tears) on the fabric this may have concentrated the force at the corners of these tears causing the material to tear further. It's difficult to say though. The tent supports may have been pulled, but I believe these were still standing when the tent was found. Was the rope still in one piece?
Overall I don't think it looks like it would support the High wind theory. Obviously a reconstruction of the tent in a wind tunnel would be a better test. Does anyone have a wind tunnel available to test the hypothesis?
Regards
Star man
sarapuk:
--- Quote from: Star man on February 25, 2019, 03:46:56 PM ---I have completed some simple calculations of wind force on the tent. I have used a formular that is used to estimate the wind loading on civil structures. I had broken it down into detail, but for some reason all my text has just vanished so here is the simple version:
F= AxPxCd
A is cross sectional area normal to wind direction
P is the wind pressure = 0.613 x V^2. V is I metres per second
Cd is the drag coefficient which is about 1.4 for a smallish rectangle
At 100 miles per hour the force on the tent would be about 870kg
At 80 miles per hour it would be about 620 Kg
Most of this force would be spread out across th fabric on the side exposed to the wind and also taken up by the tension in the rope and then transmitted to the supports that the rope is attached to.
All in all it doesn't seem that significant. For 100 miles per hour it may have been approaching the limit for the rope but probably not for the tent fabric. If there was a weak point (tears) on the fabric this may have concentrated the force at the corners of these tears causing the material to tear further. It's difficult to say though. The tent supports may have been pulled, but I believe these were still standing when the tent was found. Was the rope still in one piece?
Overall I don't think it looks like it would support the High wind theory. Obviously a reconstruction of the tent in a wind tunnel would be a better test. Does anyone have a wind tunnel available to test the hypothesis?
Regards
Star man
--- End quote ---
Thats an impressive looking calculation. But how do we know what the actual speed of the wind was when the Dyatlov group were on the mountainside ! ? And for that calculation to be of any use we would also need to know the strength of the Tent FABRIC, and where any joins in the fabric were.
Star man:
--- Quote from: sarapuk on February 25, 2019, 05:11:58 PM ---
--- Quote from: Star man on February 25, 2019, 03:46:56 PM ---I have completed some simple calculations of wind force on the tent. I have used a formular that is used to estimate the wind loading on civil structures. I had broken it down into detail, but for some reason all my text has just vanished so here is the simple version:
F= AxPxCd
A is cross sectional area normal to wind direction
P is the wind pressure = 0.613 x V^2. V is I metres per second
Cd is the drag coefficient which is about 1.4 for a smallish rectangle
At 100 miles per hour the force on the tent would be about 870kg
At 80 miles per hour it would be about 620 Kg
Most of this force would be spread out across th fabric on the side exposed to the wind and also taken up by the tension in the rope and then transmitted to the supports that the rope is attached to.
All in all it doesn't seem that significant. For 100 miles per hour it may have been approaching the limit for the rope but probably not for the tent fabric. If there was a weak point (tears) on the fabric this may have concentrated the force at the corners of these tears causing the material to tear further. It's difficult to say though. The tent supports may have been pulled, but I believe these were still standing when the tent was found. Was the rope still in one piece?
Overall I don't think it looks like it would support the High wind theory. Obviously a reconstruction of the tent in a wind tunnel would be a better test. Does anyone have a wind tunnel available to test the hypothesis?
Regards
Star man
--- End quote ---
Thats an impressive looking calculation. But how do we know what the actual speed of the wind was when the Dyatlov group were on the mountainside ! ? And for that calculation to be of any use we would also need to know the strength of the Tent FABRIC, and where any joins in the fabric were.
--- End quote ---
The call is only to allow a somewhat better judgment of the high wind theory. It doesn’t take account of a gusting wind which could have shaken the tent. But even for a high wind the forces are still survivable. In my mind a 100 mph wind should be enough to rip up an empty tent and blow it away. But it doesn’t look like it would destroy the tent with 9 people in it. Obviously it is unlikely the wind speed actually reached 100 mph but I am using 100 mph as an upper reference guide. Only a reconsideration could give a more reasonable answer.
I like to try to understand how any given theory can be positively proven or disproven given the lack of concrete evidence for the DPI
sarapuk:
--- Quote from: Star man on February 25, 2019, 11:42:14 PM ---
--- Quote from: sarapuk on February 25, 2019, 05:11:58 PM ---
--- Quote from: Star man on February 25, 2019, 03:46:56 PM ---I have completed some simple calculations of wind force on the tent. I have used a formular that is used to estimate the wind loading on civil structures. I had broken it down into detail, but for some reason all my text has just vanished so here is the simple version:
F= AxPxCd
A is cross sectional area normal to wind direction
P is the wind pressure = 0.613 x V^2. V is I metres per second
Cd is the drag coefficient which is about 1.4 for a smallish rectangle
At 100 miles per hour the force on the tent would be about 870kg
At 80 miles per hour it would be about 620 Kg
Most of this force would be spread out across th fabric on the side exposed to the wind and also taken up by the tension in the rope and then transmitted to the supports that the rope is attached to.
All in all it doesn't seem that significant. For 100 miles per hour it may have been approaching the limit for the rope but probably not for the tent fabric. If there was a weak point (tears) on the fabric this may have concentrated the force at the corners of these tears causing the material to tear further. It's difficult to say though. The tent supports may have been pulled, but I believe these were still standing when the tent was found. Was the rope still in one piece?
Overall I don't think it looks like it would support the High wind theory. Obviously a reconstruction of the tent in a wind tunnel would be a better test. Does anyone have a wind tunnel available to test the hypothesis?
Regards
Star man
--- End quote ---
Thats an impressive looking calculation. But how do we know what the actual speed of the wind was when the Dyatlov group were on the mountainside ! ? And for that calculation to be of any use we would also need to know the strength of the Tent FABRIC, and where any joins in the fabric were.
--- End quote ---
The call is only to allow a somewhat better judgment of the high wind theory. It doesn’t take account of a gusting wind which could have shaken the tent. But even for a high wind the forces are still survivable. In my mind a 100 mph wind should be enough to rip up an empty tent and blow it away. But it doesn’t look like it would destroy the tent with 9 people in it. Obviously it is unlikely the wind speed actually reached 100 mph but I am using 100 mph as an upper reference guide. Only a reconsideration could give a more reasonable answer.
I like to try to understand how any given theory can be positively proven or disproven given the lack of concrete evidence for the DPI
--- End quote ---
A KATABATIC WIND can reach 200 MPH, or hurricane force. And as you correctly say , even for high wind the forces are still survivable. The Dyatlov Tent doesnt appear to have suffered such high forces, making it even less likely that wind played a part in their leaving the Tent.
Star man:
--- Quote from: sarapuk on February 26, 2019, 11:50:44 AM ---
--- Quote from: Star man on February 25, 2019, 11:42:14 PM ---
--- Quote from: sarapuk on February 25, 2019, 05:11:58 PM ---
--- Quote from: Star man on February 25, 2019, 03:46:56 PM ---I have completed some simple calculations of wind force on the tent. I have used a formular that is used to estimate the wind loading on civil structures. I had broken it down into detail, but for some reason all my text has just vanished so here is the simple version:
F= AxPxCd
A is cross sectional area normal to wind direction
P is the wind pressure = 0.613 x V^2. V is I metres per second
Cd is the drag coefficient which is about 1.4 for a smallish rectangle
At 100 miles per hour the force on the tent would be about 870kg
At 80 miles per hour it would be about 620 Kg
Most of this force would be spread out across th fabric on the side exposed to the wind and also taken up by the tension in the rope and then transmitted to the supports that the rope is attached to.
All in all it doesn't seem that significant. For 100 miles per hour it may have been approaching the limit for the rope but probably not for the tent fabric. If there was a weak point (tears) on the fabric this may have concentrated the force at the corners of these tears causing the material to tear further. It's difficult to say though. The tent supports may have been pulled, but I believe these were still standing when the tent was found. Was the rope still in one piece?
Overall I don't think it looks like it would support the High wind theory. Obviously a reconstruction of the tent in a wind tunnel would be a better test. Does anyone have a wind tunnel available to test the hypothesis?
Regards
Star man
--- End quote ---
Thats an impressive looking calculation. But how do we know what the actual speed of the wind was when the Dyatlov group were on the mountainside ! ? And for that calculation to be of any use we would also need to know the strength of the Tent FABRIC, and where any joins in the fabric were.
--- End quote ---
The call is only to allow a somewhat better judgment of the high wind theory. It doesn’t take account of a gusting wind which could have shaken the tent. But even for a high wind the forces are still survivable. In my mind a 100 mph wind should be enough to rip up an empty tent and blow it away. But it doesn’t look like it would destroy the tent with 9 people in it. Obviously it is unlikely the wind speed actually reached 100 mph but I am using 100 mph as an upper reference guide. Only a reconsideration could give a more reasonable answer.
I like to try to understand how any given theory can be positively proven or disproven given the lack of concrete evidence for the DPI
--- End quote ---
A KATABATIC WIND can reach 200 MPH, or hurricane force. And as you correctly say , even for high wind the forces are still survivable. The Dyatlov Tent doesnt appear to have suffered such high forces, making it even less likely that wind played a part in their leaving the Tent.
--- End quote ---
At 150 mph the force on the tent would have been 2200kg, and at 200 mph the force would have been 3900 Kg
I doubt that any of the tent would have still been standing if it had been exposed to those sorts of wind speeds. I doubt that a katabatic wind of that magnitude would occur 300 metres from the sumit.
Saying that a lesser wind may still be able to tear open a poorly repaired tent.
If a katabatic wind had developed it would have flowed down into the valley below in the direction that the group went. If the wind speed was significant it should have up rooted some trees and it would not have been easy to have built the fire at the cedar. I don't believe there was any evidence of fallen trees when the search and rescue team arrived. So overall it is looking less likely, but difficult to rule out completely. To support the theory we would need to identify some way of positively confirming that high winds capable of damaging the tent were there that night. The cuts in the tent seem to be made by both tears and cuts with a sharp implement and as we know these could have been made during the tents recovery.
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