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Papers by Paul Zakrzewski
Journal of Ship Research, Dec 1, 1998
With a view to formulating vessel spraying and icing models, 22 spraying experiments were perform... more With a view to formulating vessel spraying and icing models, 22 spraying experiments were performed in the IMD/NRC towing tank using a 1:13 scale model of the stern trawler MT Zandberg. Neglecting the effect of wind drag on the spray droplet trajectories, an empirical spray flux equation for the scale Zandberg was derived, based on a statistical analysis of the spraying data. Using Froude number scaling, this model-scale equation was transformed into a full-scale spray flux equation. This spraying study shows that the total spray flux generated during ship/wave collisions depends on ship speed (Vs) and significant wave height (H1/3) according to V3⅓, H7⅓ while the spray flux distribution over the foredeck varies exponentially with longitudinal distance. Using this full-scale spray flux equation, a spray trajectory model, taking wind drag effects into account, was subsequently developed.
Wind-and wave-generated spray fluxes to an object (cylinder and vertical plate) located on and ab... more Wind-and wave-generated spray fluxes to an object (cylinder and vertical plate) located on and above the deck of a medium-sized fishing vessel (MFV) are investigated. Using formulas derived for a fully arisen sea, sea-state was defined by the significant wave height, which is a function of wind speed and fetch. Formulas for the liquid water content (LWC) of windgenerated spray are reviewed. It was found that wind-generated spray does not affect an object located on and above the deck of a MFV. Such spray may affect only small ships with low freeboard and low bows in strong winds. Wave-generated spray is the one and only source of water delivery to an object if rain, drizzle, snow, fog, and the flooding of a ship deck by waves is neglected. The wave-generated spray flux was defined using derived formulas of the vertical distribution of the LWC and time of ship exposure to spray originating from spray cloud induced by ship/wave collision. These formulas were derived using published data on a Russian field experiment in the Sea of Japan. The time-averaged water flux to an object can be computed for any given wind speed, fetch, ship speed, and heading angle. These results are applicable for calculating the ice growth rates on medium fishing vessels.
The growth of saline spongy ice due to freezing of collision-generated spray on the mast of a shi... more The growth of saline spongy ice due to freezing of collision-generated spray on the mast of a ship is modelled. The model considers the transport of brine on the icing surface and salt entrapment in the accretion. The results are applicable for calculating the effects of ice loads due to icing on ship stability.
Wind-and wave-generated spray fluxes to an object (cylinder and vertical plate) located on and ab... more Wind-and wave-generated spray fluxes to an object (cylinder and vertical plate) located on and above the deck of a medium-sized fishing vessel (MFV) are investigated. Using formulas derived for a fully arisen sea, sea-state was defined by the significant wave height, which is a function of wind speed and fetch. Formulas for the liquid water content (LWC) of windgenerated spray are reviewed. It was found that wind-generated spray does not affect an object located on and above the deck of a MFV. Such spray may affect only small ships with low freeboard and low bows in strong winds. Wave-generated spray is the one and only source of water delivery to an object if rain, drizzle, snow, fog, and the flooding of a ship deck by waves is neglected. The wave-generated spray flux was defined using derived formulas of the vertical distribution of the LWC and time of ship exposure to spray originating from spray cloud induced by ship/wave collision. These formulas were derived using published data on a Russian field experiment in the Sea of Japan. The time-averaged water flux to an object can be computed for any given wind speed, fetch, ship speed, and heading angle. These results are applicable for calculating the ice growth rates on medium fishing vessels.
Cold Regions Science and Technology, 1987
Abstract The collision-generated spray flux was defined using formulas derived for the vertical d... more Abstract The collision-generated spray flux was defined using formulas derived for the vertical distribution of the liquid water content and time of ship exposure to spray originating from the spray cloud induced by ship-wave collision. These formulas were derived using published data on a Russian field experiment in the Sea of Japan. The time-averaged water flux to an object (cylinder and vertical plate) can be computed for any given wind speed, fetch, ship speed and heading angle. The runoff of seawater from vertically oriented objects located on a ship has been investigated. The ratio between the duration of moving water film residence on the object's surface to the time interval between two successive splashings of a ship with spray has been computed for several values of wind speed, ship speed, and heading. This ratio has been used to correct the time-integrated ice growth rates on elevated objects. The results are applicable for calculating the ice loads on a ship.
Journal of the Meteorological Society of Japan. Ser. II, 1988
Maps for ship icing potential distribution over the oceans are reviewed. Special attention is pai... more Maps for ship icing potential distribution over the oceans are reviewed. Special attention is paid to maps presenting forecast icing rates on ships. The NOAA Experimental Ice Accretion map with a 24-hour categorical forecast of ice growth rate and the AES approach to mapping icing intensity are evaluated. A new mathematical model for the growth of spongy saline ice on a ship's superstructure is presented in detail. This model calculates the icing rates over the entire front face of the ship's superstructure within the zone of spraying. The effect of the salinity of the moving water film and the ice sponginess are both taken into account. The model input is the ship speed and heading, the air temperature, the seawater salinity, the sea surface temperature, and the wind speed and fetch. Computer-produced maps of the icing rates on the ship are produced for the cold waters east of Canada. The first results indicate that our new ship icing model could be applied for operational purposes (hindcasting and forecasting icing rates on ships) if an automated data acquisition system was available.
Ocean Engineering, 1988
The maximum extent of ship spraying for a medium-sized fishing trawler (MFV) of Soviet type has b... more The maximum extent of ship spraying for a medium-sized fishing trawler (MFV) of Soviet type has been considered. A simple geometrical model for generating the spray due to ship-wave collisions has been applied to determine the maximum height of the spray source above the ship deck. The maximum height of the spray source has been assumed to depend on the ship speed relative to the moving waves and an empirical constant specific to a given type of ship. A unique field data set (Kuzniecov et al., 1971) of the height of the upper limit of ice accretion on the foremast of an MFV has been used to determine the value of the empirical constant for this vessel. For documented air-sea and ship motion parameters, the trajectories of droplets hitting the upper parts of the accretion on the foremast have been calculated using the equation of droplet motion for each reported icing event. The heights of the spray source computed by the trajectory method for each case of icing were compared with the heights of the spray source determined by a correlation involving the ship speed relative to the waves and the vertical extent of spray. The best fit was obtained for an empirical constant value of 0.535. The model performance was tested using an independent data set (Sharapov, 1971) on the spraying zone of an MFV. The tests showed that this model predicts the extent of the spraying zone over the ship with satisfactory accuracy and suggest that it should be incorporated into an integrated ship icing model. Finally, the model was run for several ship speeds, headings and wind speeds to examine the effect of these parameters on the maximum height of the spray hitting the ship's foremast. It was found that this height increases with wind speed and ship speed and is maximum for ship headings of 120-130 ° .
Journal of Ship Research, Dec 1, 1998
With a view to formulating vessel spraying and icing models, 22 spraying experiments were perform... more With a view to formulating vessel spraying and icing models, 22 spraying experiments were performed in the IMD/NRC towing tank using a 1:13 scale model of the stern trawler MT Zandberg. Neglecting the effect of wind drag on the spray droplet trajectories, an empirical spray flux equation for the scale Zandberg was derived, based on a statistical analysis of the spraying data. Using Froude number scaling, this model-scale equation was transformed into a full-scale spray flux equation. This spraying study shows that the total spray flux generated during ship/wave collisions depends on ship speed (Vs) and significant wave height (H1/3) according to V3⅓, H7⅓ while the spray flux distribution over the foredeck varies exponentially with longitudinal distance. Using this full-scale spray flux equation, a spray trajectory model, taking wind drag effects into account, was subsequently developed.
Wind-and wave-generated spray fluxes to an object (cylinder and vertical plate) located on and ab... more Wind-and wave-generated spray fluxes to an object (cylinder and vertical plate) located on and above the deck of a medium-sized fishing vessel (MFV) are investigated. Using formulas derived for a fully arisen sea, sea-state was defined by the significant wave height, which is a function of wind speed and fetch. Formulas for the liquid water content (LWC) of windgenerated spray are reviewed. It was found that wind-generated spray does not affect an object located on and above the deck of a MFV. Such spray may affect only small ships with low freeboard and low bows in strong winds. Wave-generated spray is the one and only source of water delivery to an object if rain, drizzle, snow, fog, and the flooding of a ship deck by waves is neglected. The wave-generated spray flux was defined using derived formulas of the vertical distribution of the LWC and time of ship exposure to spray originating from spray cloud induced by ship/wave collision. These formulas were derived using published data on a Russian field experiment in the Sea of Japan. The time-averaged water flux to an object can be computed for any given wind speed, fetch, ship speed, and heading angle. These results are applicable for calculating the ice growth rates on medium fishing vessels.
The growth of saline spongy ice due to freezing of collision-generated spray on the mast of a shi... more The growth of saline spongy ice due to freezing of collision-generated spray on the mast of a ship is modelled. The model considers the transport of brine on the icing surface and salt entrapment in the accretion. The results are applicable for calculating the effects of ice loads due to icing on ship stability.
Wind-and wave-generated spray fluxes to an object (cylinder and vertical plate) located on and ab... more Wind-and wave-generated spray fluxes to an object (cylinder and vertical plate) located on and above the deck of a medium-sized fishing vessel (MFV) are investigated. Using formulas derived for a fully arisen sea, sea-state was defined by the significant wave height, which is a function of wind speed and fetch. Formulas for the liquid water content (LWC) of windgenerated spray are reviewed. It was found that wind-generated spray does not affect an object located on and above the deck of a MFV. Such spray may affect only small ships with low freeboard and low bows in strong winds. Wave-generated spray is the one and only source of water delivery to an object if rain, drizzle, snow, fog, and the flooding of a ship deck by waves is neglected. The wave-generated spray flux was defined using derived formulas of the vertical distribution of the LWC and time of ship exposure to spray originating from spray cloud induced by ship/wave collision. These formulas were derived using published data on a Russian field experiment in the Sea of Japan. The time-averaged water flux to an object can be computed for any given wind speed, fetch, ship speed, and heading angle. These results are applicable for calculating the ice growth rates on medium fishing vessels.
Cold Regions Science and Technology, 1987
Abstract The collision-generated spray flux was defined using formulas derived for the vertical d... more Abstract The collision-generated spray flux was defined using formulas derived for the vertical distribution of the liquid water content and time of ship exposure to spray originating from the spray cloud induced by ship-wave collision. These formulas were derived using published data on a Russian field experiment in the Sea of Japan. The time-averaged water flux to an object (cylinder and vertical plate) can be computed for any given wind speed, fetch, ship speed and heading angle. The runoff of seawater from vertically oriented objects located on a ship has been investigated. The ratio between the duration of moving water film residence on the object's surface to the time interval between two successive splashings of a ship with spray has been computed for several values of wind speed, ship speed, and heading. This ratio has been used to correct the time-integrated ice growth rates on elevated objects. The results are applicable for calculating the ice loads on a ship.
Journal of the Meteorological Society of Japan. Ser. II, 1988
Maps for ship icing potential distribution over the oceans are reviewed. Special attention is pai... more Maps for ship icing potential distribution over the oceans are reviewed. Special attention is paid to maps presenting forecast icing rates on ships. The NOAA Experimental Ice Accretion map with a 24-hour categorical forecast of ice growth rate and the AES approach to mapping icing intensity are evaluated. A new mathematical model for the growth of spongy saline ice on a ship's superstructure is presented in detail. This model calculates the icing rates over the entire front face of the ship's superstructure within the zone of spraying. The effect of the salinity of the moving water film and the ice sponginess are both taken into account. The model input is the ship speed and heading, the air temperature, the seawater salinity, the sea surface temperature, and the wind speed and fetch. Computer-produced maps of the icing rates on the ship are produced for the cold waters east of Canada. The first results indicate that our new ship icing model could be applied for operational purposes (hindcasting and forecasting icing rates on ships) if an automated data acquisition system was available.
Ocean Engineering, 1988
The maximum extent of ship spraying for a medium-sized fishing trawler (MFV) of Soviet type has b... more The maximum extent of ship spraying for a medium-sized fishing trawler (MFV) of Soviet type has been considered. A simple geometrical model for generating the spray due to ship-wave collisions has been applied to determine the maximum height of the spray source above the ship deck. The maximum height of the spray source has been assumed to depend on the ship speed relative to the moving waves and an empirical constant specific to a given type of ship. A unique field data set (Kuzniecov et al., 1971) of the height of the upper limit of ice accretion on the foremast of an MFV has been used to determine the value of the empirical constant for this vessel. For documented air-sea and ship motion parameters, the trajectories of droplets hitting the upper parts of the accretion on the foremast have been calculated using the equation of droplet motion for each reported icing event. The heights of the spray source computed by the trajectory method for each case of icing were compared with the heights of the spray source determined by a correlation involving the ship speed relative to the waves and the vertical extent of spray. The best fit was obtained for an empirical constant value of 0.535. The model performance was tested using an independent data set (Sharapov, 1971) on the spraying zone of an MFV. The tests showed that this model predicts the extent of the spraying zone over the ship with satisfactory accuracy and suggest that it should be incorporated into an integrated ship icing model. Finally, the model was run for several ship speeds, headings and wind speeds to examine the effect of these parameters on the maximum height of the spray hitting the ship's foremast. It was found that this height increases with wind speed and ship speed and is maximum for ship headings of 120-130 ° .