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Vertical positioning in waves Power, J.; Simões Ré, A.
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DOCUMENTATION PAGE REPORT NUMBER
TR-2011-06
NRC REPORT NUMBER DATE April 2011 REPORT SECURITY CLASSIFICATION
Unclassified
DISTRIBUTION Unlimited Title
VERTICAL POSITIONING IN WAVES
AUTHOR(S)
J. Power and A. Simões Ré
CORPORATE AUTHOR(S)/PERFORMING AGENCY(S)
Institute for Ocean Technology, National Research Council, St. John’s, NL PUBLICATION
SPONSORING AGENCY(S)
Petroleum Research Atlantic Canada (PRAC) IOT PROJECT NUMBER
42-2448-26
NRC FILE NUMBER
KEY WORDS
Immersion suit, vertical, waves
PAGES vi, 13 FIGS. 3 TABLES 3 SUMMARY
Current CGSB testing standards (CAN/CGSB:65.17-1999) require that participants be able to move to a vertical position in calm water tests only. The effect that two separate wave frequencies had on the ability of people to move to a vertical position was investigated. Twenty-three participants were instructed to move to a vertical position in the following conditions: calm water, a regular wave spectrum, and an irregular wave spectrum. There were no significant differences in the length of time it took to move to a vertical position across all three conditions. Visual observations of the participants in the water suggest that more physical effort was required on their part to stabilize themselves while in waves. Two participants were unable to move to a vertical position in calm water. In conclusion, the two wave spectrums tested increased the amount of physical effort required by the participants to remain in a vertical position, but did not significantly affect the time it took to do so.
ADDRESS National Research Council Institute for Ocean Technology Arctic Avenue, P. O. Box 12093 St. John's, NL A1B 3T5
National Research Council Conseil national de recherches Canada Canada Institute for Ocean Institut des technologies Technology océaniques
VERTICAL POSITIONING IN WAVES
TR-2011-06
Jonathan Power António Simões Ré
ACKNOWLEDGEMENTS
The research team would like to thank Petroleum Research Atlantic Canada (PRAC) for their financial support of this work.
We would also like to thank all the exceptionally talented staff at NRC-IOT who were involved in this project for their hard work and effort. The project would never have been completed if it were not for their creative, insightful input and dedicated support.
Last, but certainly not least, we would like to extend a very big thank you to all the participants who volunteered for this study. All the participants were a pleasure to work with thanks to the positive, accommodating attitude they had during the experiment.
TABLE OF CONTENTS Acknowledgements... iii 1.0 INTRODUCTION...1 2.0 METHODS ...1 2.1 Test Facility ...2 2.2 Waves...2 2.3 Instrumentation ...2
2.4 Helicopter Passenger Transportation Suit...3
3.0 PROCEDURE ...3
3.1 Statistical Analyses ...6
4.0 RESULTS ...6
5.0 DISCUSSION ...7
6.0 REFERENCES...8
APPENDIX A: Raw Participant Data APPENDIX B: Wave Data LIST OF TABLES Table 2.0 Participant anthropometrics (Mean ± Standard Deviation) ...2
Table 3.0: Suit sizing chart ...4
Table 4.1: Time (Mean ± SD) to achieve a vertical position...6
LIST OF FIGURES Figure 2.0: Diagram of CWTT located at NRC-IOT. ...2
Figure 2.1: Helicopter passenger transportation suit...3
VERTICAL POSITIONING IN WAVES 1.0 INTRODUCTION
It has long been thought that the majority of fatalities that occur after immersion in cold water were attributed to hypothermia (a 2°C or greater drop in deep body temperature). However, there have been reported cases of people perishing in cold water after being immersed for only a few minutes, often less than 10m from shore. It is now known that a series of physiological responses termed the Cold Shock Response (CSR) is responsible for the majority of deaths upon initial immersion in cold water [3].
An immersion suit is a life saving appliance that is designed to reduce the magnitude of the CSR upon sudden immersion in cold water, delay the onset of hypothermia, and provide acceptable flotation for the wearer. Immersion suits in Canada can be split into two different categories: Marine Abandonment Suits [2] and Helicopter Passenger Transportation Suits (HPTS) [1]. Both styles of suits are required to meet specific Canadian General Standards Board (CGSB) standards before they can be approved for use.
At the CGSB meeting in November of 2009, committee members reviewed CAN/CGSB-65.17-99 and a working group was created to address a number of identified potential issues with the current version of the standard. One of the issues identified was that the current version of CAN/CGSB-65.17-99 prescribed that flotation and vertical positioning tests be conducted in calm water. The working group identified that testing only in calm water may not give an accurate indication of performance in waves. In the fall of 2010, Petroleum Research Atlantic Canada (PRAC) asked the National Research Council of Canada’s Institute for Ocean Technology (NRC-IOT) to investigate the change in performance of an approved HPTS when moving from the current prescribed calm water testing to conditions with waves. This report describes the vertical positioning portion of the tests.
2.0 METHODS
Twenty-three healthy males and females volunteered to participate in this study. The National Research Council of Canada’s Research Ethics Board reviewed and approved the protocol for this study (REB#:2010-65). Participant anthropometrics is given in Table 2.0.1
1
Table 2.0 Participant anthropometrics (Mean ± Standard Deviation)
n = 23 Age (yo) Height (cm) Weight (kg) Body Fat %
Female (n= 4) 29.0 ± 12.2 165.5 ± 7.9 70.7 ± 9.3 35.1 ± 4.2
Male (n= 19) 26.3 ± 7.5 180.0 ± 6.8 85.0 ± 14.6 19.8 ± 6.3
Overall 26.8 ± 8.2 177.4 ± 8.8 82.5 ± 14.7 22.5 ± 8.3
2.1 Test Facility
All tests were carried out at the NRC-IOT Clear Water Towing Tank (CWTT) located in St. John’s, Canada. The CWTT is a 200m long, 12m wide, and 12m deep towing tank that has a dual flap wave maker located on the west end of the tank, capable of generating uni-directional waves. The waves travel down the CWTT in a west to east direction, and are absorbed by beach located at the east end.
Figure 2.0: Diagram of CWTT located at NRC-IOT.
A motorized carriage runs along a set of rails located on either side of the CWTT, and is capable of traveling of speeds up to 10 m·s-1.
2.2 Waves
Two separate wave spectrums were used during the test program2. The first was a regular wave spectrum with a maximum height of 0.69m with a period of 3 seconds.. The second was a 2-min irregular JONSWAP spectrum with a maximum wave height of 0.41m.
2.3 Instrumentation
Wave height was measured using custom fabricated capacitance probes at two locations: upstream approximately 20m east of the wave maker; and one attached directly to the CWTT carriage directly across from the location of the participant.
2
Video recordings of the participants were made throughout the test program by digital video recorders located in three locations: overhead the participants looking down at an angle at the participants; directly across from them above the surface of the water; and directly across from them just below the surface of the water.
The time for the participants to transition from a supine to vertical position was measured using a digital stopwatch controlled by a member of the research team.
The participants weight and body fat percentage were measured using a bio-electrical impedance scale manufactured by Tanita Corporation (Arlington Heights, IL, USA).
2.4 Helicopter Passenger Transportation Suit
All participants wore a face seal style helicopter passenger transportation suit3 that was approved to the CGSB standard: CAN/CGSB-65.17-99 as seen in Figure 2.1.
Figure 2.1: Helicopter passenger transportation suit.
3.0 PROCEDURE
Upon arrival at NRC-IOT participants were instructed to change into a long sleeved cotton shirt and denim jeans. After changing into the test clothing, the participants height, weight, and body fat percentage were measured. After recording the participant’s anthropometric measurements, an appropriate suit size was selected for them based on their height, referencing the sizing chart of the suit manufacturer (Table 3.0.). Small suits were not available for use during the test program. Participants who required a small suit wore an extra small size suit.
3
Table 3.0: Suit sizing chart
The participant partially donned the HPTS and proceeded to the CWTT. On the beach of the CWTT a research team member provided a verbal explanation to the participant about the tests and how to move into a vertical position in the water. After the explanation was given, the research team member proceeded to help the participant fully don the suit. The front zipper was fully zipped, and the Velcro straps located on the wrist cuffs of the suit were secured. The gloves were not worn for the tests.
The participant slowly entered the water by walking down the beach of the CWTT and transitioned to a supine position in the water. Participants were given the opportunity to practice moving to, and maintaining, a vertical position in calm water near the beach. If they were unable to transition to a vertical position in the calm water practice, the test ended and they exited the water. If the participant was able to move to a vertical position, and indicated that they were comfortable with the maneuver, they took hold of a float connected to the CWTT carriage and were towed to the west end of the tank to begin the test (Figure 3.1).
Figure 3.1: Participant under tow by the CWTT carriage.
Once in position, the participant was given a brief rest period prior to the start of the tests. The first test required the participants to achieve a vertical position in calm water. The participant started in the supine position, and upon instruction from a research team member watching on the CWTT from above, attempted to move into a vertical position. The research team member watching above used a digital stop watch to measure the time it took the participant to move from their back to when they had their feet directly underneath them, indicating that they had achieved a vertical position in the water. Participants were instructed to hold this position for 1 minute and then to move back into a supine position for a brief rest period.
The order that the participant experienced the two different wave spectrums (regular and irregular) was alternated. After the participant indicated that they were ready to begin again, wave generation began. The research team member waited until at least two waves passed by the participant, and then instructed them to move to a vertical position in the waves. The time it took to transition to a vertical position was recorded in the same fashion as described for the calm tests. Participants were required to maintain a vertical position for 1 minute in the waves. After successfully holding the vertical position for 1 minute, the wave generation was stopped, and the participant was instructed to return to a supine position and was given a brief rest. This procedure was then repeated for the next set of waves. Once both sets of waves were completed, the participant was towed back to the beach of the CWTT and then exited the water.
3.1 Statistical Analyses
The Shapiro Wilks test was used to test for normal distribution. A within participant, repeated measures study design was used for this experiment. Analysis of variance (ANOVA) was performed on all collected results. Tamahrene T2 post hoc tests were performed to determine significance, with a P value of less than 0.05 considered as significant.
4.0 RESULTS
Twenty-one of the twenty-three participants were able to achieve a vertical position in the calm water practice. The two females who were unable to stand upright in the water were also the two shortest participants in the entire group (157cm, and 163cm). One male participant had significant difficulty in standing up in the Regular wave condition, but no difficult in the other two conditions. As a result of the large discrepancy in the times, his data were dropped from the analysis.
The time it took for the participants to achieve a vertical position in the three test conditions (Calm, Regular Waves, Irregular Waves) is given in Table 4.1.
Table 4.1: Time (Mean ± SD) to achieve a vertical position.
n = 20 Calm (s) Regular Waves (s) Irregular Waves (s) Female (n = 2) 4.9 ± 2.7 3.8 ± 2.5 3.0 ± 1.7 Male (n = 18) 3.8 ± 1.8 3.3 ± 1.4 2.9 ± 1.2 Overall (n = 20) 3.9 ± 1.8 3.3 ± 1.4 2.9 ± 1.2
There were no significant differences in the time to achieve a vertical position across all three tests conditions.
5.0 DISCUSSION
The results collected from this experiment show that the two wave spectrums used did not hinder the ability of the participants to achieve vertical positions when compared to calm water. The overall mean average time to achieve a vertical position was very similar across all three conditions; with the largest difference being approximately one second between the Calm and Irregular wave condition.
Visual observations of the participants while they were performing the tests suggested that the wave conditions posed a greater physical challenge to maintain an upright position in the water. Many participants used treading water motions with their arms and continuously kicked their legs while in the waves. These stabilizing actions suggest that the waves used in this test were impacting their balance in the water, but not to the point where the participants where unable to compensate for it.
Two of the recruited participants where not able to achieve a vertical position during the calm water practice sessions. Both participants reported a great amount of difficulty in trying to bring their feet under the water. They said that the boots felt too big and cumbersome, and that they were not able to overcome the resultant buoyancy. These two participants were also the shortest of those recruited. It is not known if the reason for these two participants to achieve a vertical position was due to their height, the inability to generate the necessary force to pull the boots under the water, or a lack of skill in the maneuver.
Two participants performed tests in two additional wave spectrums at the end of the test program. One wave spectrum consisted of regular, small, high frequency waves. Both participants were able to maintain a vertical position in this spectrum with little difficulty. The second spectrum was the same wave height used for the Regular waves, the period of the waves was shortened from 3 to 2 seconds. These waves proved to be extremely challenging to both participants, and with one participants becoming submerged multiple times while maintaining a vertical position. Both participants had to actively work to stay upright in the water and propel themselves upwards in time with the oncoming waves. After test was completed, both participants reported feeling tired due to the level of physical activity required to stay upright and above the water surface in the waves.
In conclusion, the two wave spectrums tested in this experiment did not affect the ability for the participants to achieve, and maintain a vertical position, when compared to calm water. The time it took to transition to a vertical position was not significantly different across all the test conditions. Visual observations of the participants above and below water suggested that the participants only required minimum physical effort to maintain the balance when upright in the water for the three test conditions. Of the two additional wave spectrums tested, one proved to be extremely challenging for the two participants to stay upright and above the water surface. This challenging wave spectrum was only 1 second faster than the Regular waves experienced by the 21 other participants. Since the height of the waves did not change, only the rate at which they passed by the 2 participant, this suggests that the frequency of the waves may be a significant factor in adding to the challenge of maintaining a vertical position. It is possible that specific
wave frequencies may increase the challenge, or completely hinder the ability, of staying upright and above the surface of the water.
6.0 REFERENCES
1. Helicopter Passenger Transportation Suit Systems. CAN/CGSB-65.17-99. Canadian General Standards Board. 1999.
2. Immersion Suit Systems. CAN/CGSB-65.16-2005. Canadian General Standards Board. 2005.
3. Tipton, M.J., The initial responses to cold-water immersion in man. Clin Sci (Lond),
APPENDIX A Raw Participant Data
APPENDIX A – RAW PARTICIPANT DATA
Females Age (yo) Height
(cm) Weight (kg) Body Fat (%) Suit Size
Time to Vertical Position (s) Calm Regular
Waves
Irregular Waves
25 176 69.5 37.1 XS 3 2 1.8
47 163 79.1 39.6 XS N/A N/A N/A
20 166 76.1 33.6 XS 6.87 5.5 4.18
24 157 58.2 29.9 XS N/A N/A N/A
Males Age (yo) Height
(cm) Weight (kg) Body Fat (%) Suit Size
Time to Vertical Position (s)
Calm Regular Waves Irregular Waves 30 178 92.7 18.4 M 4.7 3.8 4.6 34 190 99.7 21.5 L 5.0 5.2 3.4 19 168 87.8 31.2 M 4.2 2.8 3.4 26 179 76.1 16.6 M 2.3 3.2 2.9 47 176 93.1 30.2 M 2.1 4.3 4.1 30 189 100.8 23 L 2 2.1 1.5 30 180 77.9 19.1 M 4.4 4.3 1.8 24 178 116.1 28.5 M 3.2 3.5 3 22 178 62 9 M 1.9 1.7 1.5 21 183 77.3 13.2 M 1.4 1 1 22 186 86.7 20.2 M 3 1.2 1.2 19 170 54.8 8.5 XS 4.5 4.2 4.7 39 180 95.9 21.7 M 7 41 5.7 24 176 72.6 18.1 M 9.1 1.9 2.5 23 179 93.4 24.3 M 4.5 2.2 3 22 192 89.4 14.1 L 3.1 3.6 2.6 21 187 90.7 23 L 4.8 4.3 4.7 22 181 74 16.2 M 5.4 5.6 3.8 23 169 73.6 19.6 M 3.3 4.4 3.1
APPENDIX B
