Effective Crosswind Effective PAT in Still Air

Dubai A reasonable dataset is available for the Dubai region. Dubai is relatively well exposed to the northerly winds that tend to blow down the Gulf for much of the year. The calmest conditions tend to occur in winter December to February when the weather systems force a weak ridge over the central and southern Gulf. Also during the passage of the ITCZ across the region separating the northerlies from the south easterlies that tend to blow up the Gulf of Oman during the height of the SW Monsoon through the Arabian Sea. This occurs twice - once in July as it moves northwards and again in September as it returns to the south, with a slight decrease in the number of calms in August compared to the months either side. These calms are likely to be persistent and coincide with high wet bulb episodes. Fujairah This dataset looks suspicious in the fact that there is a very large variation in the number of observations from one month to the next. It is apparent that there is a relatively high incidence of light wind episodes in the Fujairah region. During the winter months this region tends to sit under a weak ridge. During summer, the ITCZ passes over the region twice. It tends to be sheltered from the prevailing northerly winds that blow down the Gulf proper and is far enough up the Gulf to be out of the core of the prevailing SE winds during the height of the SW Monsoon. Muscat The region off Muscat has one of the best sets of wind data available. However, the port itself tends to be a little more sheltered than these data would tend to indicate as it sits in the lee of a point to the south east that shelters it from the prevailing south easterlies during the SW Monsoon. Muscat is subject to calm conditions year round as there tends to be poor assistance to the sea breeze from the prevailing weather patterns. The windiest months are July and August when the SW Monsoon is at its peak - assisting the SE airflow up the Gulf of Oman. This dies away quickly with October and November being the calmest time of the year with calm conditions close to 20 of the time. During other times of the year there is likely to be a weak pressure gradient over the region. However, on most occasions a sea breeze can be expected during the afternoon, dying out quickly at sunset.

7.3 Open Deck Operation Guidelines

While the guidelines follow the same method for all open decks, limits are different for different deck widths and different animals. The descriptive material below is covered more precisely in Section 5.4, however the tables and descriptions can assist in understanding the issues.

7.3.1 Effective Crosswind

As mentioned earlier, the orientation of the dock relative to the breeze is very important in determining the crosswind. The effective crosswind to be used in this assessment is simply the windspeed multiplied by the sine of the angle between the wind direction and the ship’s keel line: V effective = Vsin wind angle That is; a wind directly along the vessel generates no crosswind, while one from the beam wind angle = 90 o is 100 crosswind sinwind angle = 1. While this can be evaluated readily on a calculator, the factor sinwind angle to go from wind speed to effective crosswind is also tabulated below for wind angles in steps of 10 o . Project: LIVE.116 – Development of a Heat Stress Risk Management Model Revision F Maunsell Australia Pty Ltd Page 54 of 129 Final Report December 2003 Table 7.1 Crosswind factor sinwind angle Wind Angle from Keel Line Crosswind Factor 10 0.17 20 0.34 30 0.50 40 0.64 50 0.77 60 0.87 70 0.94 80 0.98 90 1.0 For example; a 10 knot breeze from 20 o port or starboard of the bow or stern gives an effective crosswind of 10 x 0.34 = 3.4 knots 1.7ms.

7.3.2 Effective PAT in Still Air

As shown by the CFD, the animal heat generates buoyancy driven flows which cause some air exchange. With zero wind, the hot plume leaves the deck ceiling on both sides for example; Figure C.35 and would be reingested into the deck above. In this way, successively higher decks would get hotter and hotter the effective PAT approaches zero. With more than one open deck one tier cattle or one, or more than one, two tier sheep deck, risk levels may become unacceptable if crosswinds are so low that the plume leaves both sides of the deck. Table 7.2 gives the minimum crosswind required to ensure through ventilation, with no exhaust on the upwind side for example; Figure C.39. Table 7.2 Minimum Crosswind for Through Ventilation Minimum Crosswind Deck Width m ms knots 18 1.0 2.0 24 1.2 2.4 30 1.4 2.8 36 1.6 3.2 The consequences for higher decks at crosswinds below this are given in Section 5.4.1.

7.3.3 Effective PAT in Light Crosswinds