Thunderhead Engineering Forum

Please login or register.

Login with username, password and session length
Advanced search  

News:

Forum moved to https://forum.thunderheadeng.com

Author Topic: validation of a simple case  (Read 2352 times)

jaume

  • New Member
  • *
  • Posts: 2
    • View Profile
validation of a simple case
« on: May 18, 2016, 04:15:42 am »

I simulate the evacuation of a crowded room (2 per/m2) through a narrow door (1 m wide) with Pathfinder and another well-known commercial simulator. I use the same parameters in both cases (geometry, number of occupants, preferred free speed and shoulder width). I randomize the position of the occupants and repeat the simulation several times to calculate time average and standard deviation. The evacuation time calculated with Pathfinder (steering mode) is larger than the time calculated with the other simulator (9,28±0,15 and 5,80±0,05). I search for validation documents to decide which simulator I can trust but I only find the Verification and Validation guide of Pathfinder which does not solve my problem. Has the evacuation of a crowded room through a narrow door been validated for Pathfinder using experimental data?

Thank you.
Logged

swenson

  • Thunderhead
  • *****
  • Posts: 22
    • View Profile
Re: validation of a simple case
« Reply #1 on: June 01, 2016, 08:06:37 am »

Let me try to help.

Our Pathfinder Verification and Validation manual is available at: http://www.thunderheadeng.com/pathfinder/resources/

First, we regard the SFPE flow calculations (Human Behavior in Fire, June 2003, Society of Fire Protection Engineers) as validation data. The equations used in these calculations (see attached image) are based on experimental data. You can download a spreadsheet at the link given above. The Equations tab of the spreadsheet provides the equations. Further details are discussed in the SFPE Handbook of Fire Protection Engineering, 5th edition, chapter 59.

For a 1 m wide door, the SFPE flow rate is calculated as 0.92 pers/s. Using the number of people in the room, you can compare this calculation with the simulators you are testing. We provide SFPE calculation results for most of the validation problems described in the Verification and Validation manual (in particular, see "Chapter 3: Flow Rate Tests").

The experiments of Jun Zhang and Armin Seyfried described in "Chapter 2: Fundamental Diagram Tests" of the Pathfinder Verification and Validation manual can also be used to calculate the flow rates through a door. Their experimental data (see attached) shows a maximum specific flow of 1.5 pers/m-s at a density of about 1.8 pers/m^2 and was obtained by measuring the speed and density in a 3 m wide corridor. Flow in the corridor was controlled by adjusting the corridor entry and exit widths. If you take the same approach as used by SFPE, the door flow rate for a 1 m wide door with a 0.15 boundary layer would be 1.05 pers/s.

Both the Zhang and Seyfried paper and the Pathfinder manual present the results using the fundamental diagram.  I went back and looked at our calculations. The highest specific flow through a door that we calculated was about 1.7 pers/s-m (assuming a zero boundary layer) for the case with a 3 m entrance and 2.2 m exit. The corridor specific flow for this case was 1.27 pers/m-s at a density of 2.22 pers/m^2, so this is a case in which the corridor specific flow is in the region of high density where the specific flow is dropping (a region of experimental uncertainty). Using our calculated specific flow with no boundary layer value, the maximum flow rate for a 1 m door based indirectly on Zhang and Seyfried results would be a flow rate of 1.7 pers/s. If we assume the same 0.15 m boundary layer as in the SFPE calculations, the adjusted specific flow for the 2.2 m exit becomes 1.97 pers/s-m and a 1 m wide door would have a flow rate of 1.37 pers/s. I have not seen any door flow rate data from Zhang and Seyfried, but you might want to ask if they could provide it.

In general, the Zhang and Seyfried data would be expected to give higher flow rates, since the persons represented a younger age group.

The bottom line is that the results obtained with Pathfinder in Steering mode will reflect the assumed maximum speed and speed density profile. If you use the values that correspond to the SFPE data, you approximately recover the corresponding SFPE exit times. If you use the faster Zhang and Seyfried input, then you recover faster exit times. If you select SFPE mode, then the door flow rates will match the SFPE equations.

I will post the Pathfinder input files to our web site.

Sincerely,

Daniel Swenson
Thunderhead Engineering
Logged

jaume

  • New Member
  • *
  • Posts: 2
    • View Profile
Re: validation of a simple case
« Reply #2 on: June 15, 2016, 03:31:50 am »

Thank you for your reply.

The number of people in the room is 600, the room is 30x10 m2. I’ve repeated the simulation with Pathfinder in SFPE mode and I have obtained 4,58±0,00 min which is closer to the result obtained with the other commercial simulator (5,80 ±0,05) and differs with the calculation with Pathfinder in Steering mode (9,28±0,15). Viewing the simulations the Steering mode looks much more realistic than the SFPE mode (people don’t step on each other, don’t move like an army...) I’m a bit confused with your reply. Which Pathfinder mode should I trust, the SFPE mode or the Steering mode?
Logged

Charlie Thornton

  • Thunderhead
  • *****
  • Posts: 851
    • View Profile
Re: validation of a simple case
« Reply #3 on: June 22, 2016, 10:17:41 am »

On the topic of which mode to trust - our objective is to produce code that produces an accurate rendition of a particular model. The responsibility of deciding of how the performance within a certain model informs your analysis is left to you. This is why swenson described the performance of Pathfinder in relation to different data sets and models rather than which one is "best". To help you make the decision of how to use our software to inform your analysis we have provided the Technical Reference and the Verification and Validation guide.
Logged